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@@ -112,8 +112,8 @@ for a missing key or an out-of-range index, `at` throws for those too (`out_of_r
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#include <iostream>
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#include <nlohmann/json_view.hpp>
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using json_document = nlohmann::json_document;
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using json_view = nlohmann::json_view;
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using nlohmann::json_document;
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using nlohmann::json_view;
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int main()
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{
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@@ -166,7 +166,7 @@ for a missing key or an out-of-range index, `at` throws for those too (`out_of_r
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#include <iostream>
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#include <nlohmann/json_view.hpp>
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using json_document = nlohmann::json_document;
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using nlohmann::json_document;
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using json_pointer = nlohmann::json::json_pointer;
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int main()
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@@ -1,4 +1,4 @@
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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/at/" rel="canonical"><link href=../basic_json_view/ rel=prev><link href=../back/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>at - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#nlohmannbasic_json_viewat class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> at </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5"/></svg> </label> Line truncated
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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/at/" rel="canonical"><link href=../basic_json_view/ rel=prev><link href=../back/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>at - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#nlohmannbasic_json_viewat class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> at </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5"/></svg> </label> Line truncated
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<span class=n>basic_json_view</span><span class=w> </span><span class=nf>at</span><span class=p>(</span><span class=n>string_view_t</span><span class=w> </span><span class=n>key</span><span class=p>)</span><span class=w> </span><span class=k>const</span><span class=p>;</span>
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<span class=n>basic_json_view</span><span class=w> </span><span class=nf>at</span><span class=p>(</span><span class=k>const</span><span class=w> </span><span class=kt>char</span><span class=o>*</span><span class=w> </span><span class=n>key</span><span class=p>)</span><span class=w> </span><span class=k>const</span><span class=p>;</span>
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<span class=n>basic_json_view</span><span class=w> </span><span class=nf>at</span><span class=p>(</span><span class=k>const</span><span class=w> </span><span class=n>string_t</span><span class=o>&</span><span class=w> </span><span class=n>key</span><span class=p>)</span><span class=w> </span><span class=k>const</span><span class=p>;</span>
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@@ -13,8 +13,8 @@
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</code></pre></div> <ol> <li>Returns the value of the object member with key <code>key</code> -- the first one, should the key occur more than once (see <a href=../operator%5B%5D/#notes>Notes on duplicate keys</a>).</li> <li>Returns the array element at index <code>idx</code>. The template accepts every integer type except <code class=highlight><span class=kt>bool</span></code> and <code class=highlight><span class=n>std</span><span class=o>::</span><span class=kt>size_t</span></code> and forwards to the <code>size_type</code> overload, as for <a href=../operator%5B%5D/ ><code>operator[]</code></a>; a negative <code>idx</code> is out of range.</li> <li>Returns the value a <abbr title="JavaScript Object Notation">JSON</abbr> pointer <code>ptr</code> refers to, starting at this value.</li> </ol> <h2 id=parameters>Parameters<a class=headerlink href=#parameters title="Permanent link">¶</a></h2> <dl> <dt><code>key</code> (in)</dt> <dd>object key of the element to access</dd> <dt><code>idx</code> (in)</dt> <dd>index of the element to access</dd> <dt><code>ptr</code> (in)</dt> <dd><abbr title="JavaScript Object Notation">JSON</abbr> pointer to the element to access</dd> </dl> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">¶</a></h2> <ol> <li>the value of the first member with key <code>key</code></li> <li>the element at index <code>idx</code></li> <li>the value <code>ptr</code> resolves to, starting at this value</li> </ol> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">¶</a></h2> <p>Strong guarantee: there are no changes to the view or the document it refers to.</p> <h2 id=exceptions>Exceptions<a class=headerlink href=#exceptions title="Permanent link">¶</a></h2> <ol> <li>The function can throw the following exceptions, both with the same message as the corresponding call to <a href=../../basic_json/at/ ><code>BasicJsonType::at</code></a>:<ul> <li>Throws <a href=../../../home/exceptions/#jsonexceptiontype_error304><code>type_error.304</code></a> if the value is not an object.</li> <li>Throws <a href=../../../home/exceptions/#jsonexceptionout_of_range403><code>out_of_range.403</code></a> if no member has key <code>key</code>.</li> </ul> </li> <li>The function can throw the following exceptions, both with the same message as the corresponding call to <a href=../../basic_json/at/ ><code>BasicJsonType::at</code></a>:<ul> <li>Throws <a href=../../../home/exceptions/#jsonexceptiontype_error304><code>type_error.304</code></a> if the value is not an array.</li> <li>Throws <a href=../../../home/exceptions/#jsonexceptionout_of_range401><code>out_of_range.401</code></a> if <code class=highlight><span class=n>idx</span><span class=w> </span><span class=o>>=</span><span class=w> </span><span class=n>size</span><span class=p>()</span></code>.</li> </ul> </li> <li>The function can throw the following exceptions, all with the same message as the corresponding call to <a href=../../basic_json/at/ ><code>BasicJsonType::at</code></a>:<ul> <li>Throws <a href=../../../home/exceptions/#jsonexceptionparse_error106><code>parse_error.106</code></a> if an array index in <code>ptr</code> begins with <code class=highlight><span class=sc>'0'</span></code>.</li> <li>Throws <a href=../../../home/exceptions/#jsonexceptionparse_error109><code>parse_error.109</code></a> if an array index in <code>ptr</code> is not a number.</li> <li>Throws <a href=../../../home/exceptions/#jsonexceptionout_of_range401><code>out_of_range.401</code></a> if an array index in <code>ptr</code> is out of range.</li> <li>Throws <a href=../../../home/exceptions/#jsonexceptionout_of_range402><code>out_of_range.402</code></a> if a reference token is <code class=highlight><span class=s>"-"</span></code> at an array -- <code>at</code> never inserts an element, so <code class=highlight><span class=s>"-"</span></code> is always invalid.</li> <li>Throws <a href=../../../home/exceptions/#jsonexceptionout_of_range403><code>out_of_range.403</code></a> if a reference token names an object member that does not exist.</li> <li>Throws <a href=../../../home/exceptions/#jsonexceptionout_of_range404><code>out_of_range.404</code></a> if <code>ptr</code> cannot be resolved because a reference token is used on a primitive value.</li> </ul> </li> </ol> <p>None of these exceptions carry a <a href=../../macros/json_diagnostics/ ><code>JSON_DIAGNOSTICS</code></a> path: the view has no <code>BasicJsonType</code> value to point at, so the exception is created without one, even if <code>BasicJsonType</code> was built with <code>JSON_DIAGNOSTICS</code> enabled.</p> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">¶</a></h2> <ol> <li>Linear in the number of members: as for <a href=../../ordered_json/ ><code>ordered_json</code></a>, members are compared one after another, in document order, stopping at the first match. Each compaLine truncated
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<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json_view.hpp></span>
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<span class=k>using</span><span class=w> </span><span class=n>json_document</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
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<span class=k>using</span><span class=w> </span><span class=n>json_view</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_view</span><span class=p>;</span>
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<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
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<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_view</span><span class=p>;</span>
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<span class=kt>int</span><span class=w> </span><span class=nf>main</span><span class=p>()</span>
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<span class=p>{</span>
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@@ -52,7 +52,7 @@
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</code></pre></div> </details> <details class=example> <summary>Example: (3) access specified element via <abbr title="JavaScript Object Notation">JSON</abbr> pointer with bounds checking</summary> <p>The example below shows that <code>at</code> with a <abbr title="JavaScript Object Notation">JSON</abbr> pointer throws exactly the exceptions, with exactly the messages, that <a href=../../basic_json/at/ ><code>BasicJsonType::at</code></a> throws for the same pointer and the same document.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><iostream></span>
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<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json_view.hpp></span>
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<span class=k>using</span><span class=w> </span><span class=n>json_document</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
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<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
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<span class=k>using</span><span class=w> </span><span class=n>json_pointer</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json</span><span class=o>::</span><span class=n>json_pointer</span><span class=p>;</span>
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<span class=kt>int</span><span class=w> </span><span class=nf>main</span><span class=p>()</span>
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@@ -79,8 +79,8 @@ The example below reads required fields out of a service configuration with `at`
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#include <iostream>
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#include <nlohmann/json_view.hpp>
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using json_document = nlohmann::json_document;
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using json_view = nlohmann::json_view;
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using nlohmann::json_document;
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using nlohmann::json_view;
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int main()
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{
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@@ -130,7 +130,7 @@ The example below shows that `at` with a JSON pointer throws exactly the excepti
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#include <iostream>
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#include <nlohmann/json_view.hpp>
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using json_document = nlohmann::json_document;
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using nlohmann::json_document;
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using json_pointer = nlohmann::json::json_pointer;
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int main()
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@@ -48,7 +48,7 @@ Unlike [`BasicJsonType::back()`](../basic_json/back.md), which has undefined beh
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#include <iostream>
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#include <nlohmann/json_view.hpp>
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using json_document = nlohmann::json_document;
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using nlohmann::json_document;
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int main()
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{
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@@ -1,8 +1,8 @@
|
||||
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|
||||
</code></pre></div> <p>Returns the last element of an array, the last member value of an object, or the value itself if it is primitive (as for <a href=../../basic_json/back/ ><code>BasicJsonType::back()</code></a>, a primitive value is a range of one element).</p> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">¶</a></h2> <p>The last element or member value. For a primitive value (number, string, boolean), the value itself.</p> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">¶</a></h2> <p>Strong guarantee: there are no changes to the view or the document it refers to.</p> <h2 id=exceptions>Exceptions<a class=headerlink href=#exceptions title="Permanent link">¶</a></h2> <p>Throws <a href=../../../home/exceptions/#jsonexceptioninvalid_iterator214><code>invalid_iterator.214</code></a> if the view is <a href=../is_null/ >null</a> or <a href=../is_discarded/ >discarded</a>, or if it is an empty array or object.</p> <p>This exception does not carry a <a href=../../macros/json_diagnostics/ ><code>JSON_DIAGNOSTICS</code></a> path: the view has no <code>BasicJsonType</code> value to point at, so the exception is created without one, even if <code>BasicJsonType</code> was built with <code>JSON_DIAGNOSTICS</code> enabled.</p> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">¶</a></h2> <p>Linear in the size of the array or object: unlike <a href=../front/ ><code>front()</code></a>, which only ever looks at the first element, <code>back()</code> has to walk every element to find where they end, since elements are not a fixed size in the index. Constant if no element of the array is an array or object, since the elements are then adjacent in the index.</p> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">¶</a></h2> <p>Unlike <a href=../../basic_json/back/ ><code>BasicJsonType::back()</code></a>, which has undefined behavior for an empty array or object, <code>back()</code> throws <code>invalid_iterator.214</code> for an empty array, an empty object, a null value, or a discarded view.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">¶</a></h2> <details class=example> <summary>Example</summary> <p>The example below reads only the final status of a build log with <code>back()</code>. Even though <code>back()</code> is linear in the number of events (unlike <a href=../front/ ><code>front()</code></a>, which is constant), it still avoids building a <code>BasicJsonType</code> value for the events that are not needed.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><iostream></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json_view.hpp></span>
|
||||
|
||||
<span class=k>using</span><span class=w> </span><span class=n>json_document</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
|
||||
<span class=kt>int</span><span class=w> </span><span class=nf>main</span><span class=p>()</span>
|
||||
<span class=p>{</span>
|
||||
|
||||
@@ -38,7 +38,7 @@ The example below reads only the final status of a build log with `back()`. Even
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -1,20 +1,32 @@
|
||||
# <small>nlohmann::basic_json_view::</small>basic_json_view
|
||||
|
||||
```cpp
|
||||
// (1)
|
||||
basic_json_view() noexcept = default;
|
||||
|
||||
// (2) only for Mode == view_mode::editable
|
||||
basic_json_view(const basic_json_view<BasicJsonType, view_mode::read_only>& other) noexcept;
|
||||
```
|
||||
|
||||
Creates an invalid (discarded) view: [`type()`](type.md) is `#!cpp value_t::discarded` and
|
||||
[`is_discarded()`](is_discarded.md) is `#!cpp true`.
|
||||
1. Creates an invalid (discarded) view: [`type()`](type.md) is `#!cpp value_t::discarded` and
|
||||
[`is_discarded()`](is_discarded.md) is `#!cpp true`.
|
||||
2. Converts a view of a read-only document into a view of an editable document (implicitly), so that a function
|
||||
taking a [`json_editable_view`](../json_editable_view.md) accepts both. The result is a view of the same value of
|
||||
the same read-only document. See [`view_mode`](../view_mode.md) for why there is no conversion the other way.
|
||||
|
||||
This is the only constructor a caller can use directly. Every other view is obtained from a
|
||||
## Parameters
|
||||
|
||||
`other` (in)
|
||||
: a view of a read-only document with the same `BasicJsonType`
|
||||
|
||||
Apart from these, a view is obtained from a
|
||||
[`basic_json_document`](../basic_json_document/index.md), via [`root()`](../basic_json_document/root.md) or by
|
||||
navigating into a container with [`operator[]`](operator[].md), [`at`](at.md), [`front`](front.md), [`back`](back.md),
|
||||
[`find`](find.md), or iteration.
|
||||
|
||||
## Exception safety
|
||||
|
||||
No-throw guarantee: this constructor never throws exceptions.
|
||||
No-throw guarantee: these constructors never throw exceptions.
|
||||
|
||||
## Complexity
|
||||
|
||||
@@ -64,6 +76,7 @@ placeholder for "no value yet" and later be assigned a real view.
|
||||
|
||||
- [is_discarded](is_discarded.md) - return whether the view is invalid
|
||||
- [root](../basic_json_document/root.md) - the view of a document's root value
|
||||
- [view_mode](../view_mode.md) - whether a document and its views can be edited
|
||||
|
||||
## Version history
|
||||
|
||||
|
||||
@@ -1,5 +1,9 @@
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/basic_json_view/" rel="canonical"><link href=../ rel=prev><link href=../at/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>(Constructor) - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5Line truncated
|
||||
</code></pre></div> <p>Creates an invalid (discarded) view: <a href=../type/ ><code>type()</code></a> is <code class=highlight><span class=n>value_t</span><span class=o>::</span><span class=n>discarded</span></code> and <a href=../is_discarded/ ><code>is_discarded()</code></a> is <code class=highlight><span class=nb>true</span></code>.</p> <p>This is the only constructor a caller can use directly. Every other view is obtained from a <a href=../../basic_json_document/ ><code>basic_json_document</code></a>, via <a href=../../basic_json_document/root/ ><code>root()</code></a> or by navigating into a container with <a href=../operator%5B%5D/ ><code>operator[]</code></a>, <a href=../at/ ><code>at</code></a>, <a href=../front/ ><code>front</code></a>, <a href=../back/ ><code>back</code></a>, <a href=../find/ ><code>find</code></a>, or iteration.</p> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">¶</a></h2> <p>No-throw guarantee: this constructor never throws exceptions.</p> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">¶</a></h2> <p>Constant.</p> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">¶</a></h2> <p><code>basic_json_view</code> is trivially copyable (it holds two pointers), so a default-constructed view can be used as a placeholder for "no value yet" and later be assigned a real view.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">¶</a></h2> <details class=example> <summary>Example</summary> <p>The example below shows the default constructor and that a <code>basic_json_view</code> is a small, copyable handle.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><iostream></span>
|
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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/basic_json_view/" rel="canonical"><link href=../ rel=prev><link href=../at/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>(Constructor) - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> (Constructor) </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 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1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5Line truncated
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<span class=n>basic_json_view</span><span class=p>()</span><span class=w> </span><span class=k>noexcept</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=k>default</span><span class=p>;</span>
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||||
<span class=c1>// (2) only for Mode == view_mode::editable</span>
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||||
<span class=n>basic_json_view</span><span class=p>(</span><span class=k>const</span><span class=w> </span><span class=n>basic_json_view</span><span class=o><</span><span class=n>BasicJsonType</span><span class=p>,</span><span class=w> </span><span class=n>view_mode</span><span class=o>::</span><span class=n>read_only</span><span class=o>>&</span><span class=w> </span><span class=n>other</span><span class=p>)</span><span class=w> </span><span class=k>noexcept</span><span class=p>;</span>
|
||||
</code></pre></div> <ol> <li>Creates an invalid (discarded) view: <a href=../type/ ><code>type()</code></a> is <code class=highlight><span class=n>value_t</span><span class=o>::</span><span class=n>discarded</span></code> and <a href=../is_discarded/ ><code>is_discarded()</code></a> is <code class=highlight><span class=nb>true</span></code>.</li> <li>Converts a view of a read-only document into a view of an editable document (implicitly), so that a function taking a <a href=../../json_editable_view/ ><code>json_editable_view</code></a> accepts both. The result is a view of the same value of the same read-only document. See <a href=../../view_mode/ ><code>view_mode</code></a> for why there is no conversion the other way.</li> </ol> <h2 id=parameters>Parameters<a class=headerlink href=#parameters title="Permanent link">¶</a></h2> <dl> <dt><code>other</code> (in)</dt> <dd>a view of a read-only document with the same <code>BasicJsonType</code></dd> </dl> <p>Apart from these, a view is obtained from a <a href=../../basic_json_document/ ><code>basic_json_document</code></a>, via <a href=../../basic_json_document/root/ ><code>root()</code></a> or by navigating into a container with <a href=../operator%5B%5D/ ><code>operator[]</code></a>, <a href=../at/ ><code>at</code></a>, <a href=../front/ ><code>front</code></a>, <a href=../back/ ><code>back</code></a>, <a href=../find/ ><code>find</code></a>, or iteration.</p> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">¶</a></h2> <p>No-throw guarantee: these constructors never throw exceptions.</p> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">¶</a></h2> <p>Constant.</p> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">¶</a></h2> <p><code>basic_json_view</code> is trivially copyable (it holds two pointers), so a default-constructed view can be used as a placeholder for "no value yet" and later be assigned a real view.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">¶</a></h2> <details class=example> <summary>Example</summary> <p>The example below shows the default constructor and that a <code>basic_json_view</code> is a small, copyable handle.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><iostream></span>
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||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json_view.hpp></span>
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<span class=kt>int</span><span class=w> </span><span class=nf>main</span><span class=p>()</span>
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@@ -18,4 +22,4 @@
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<span class=p>}</span>
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||||
</code></pre></div> <p>Output:</p> <div class=highlight><pre><span></span><code><span class=kc>true</span>
|
||||
<span class=kc>true</span>
|
||||
</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">¶</a></h2> <ul> <li><a href=../is_discarded/ >is_discarded</a> - return whether the view is invalid</li> <li><a href=../../basic_json_document/root/ >root</a> - the view of a document's root value</li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">¶</a></h2> <ul> <li>Added in version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="October 21, 2026 08:21:27 UTC">October 21, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright © 2013-2026 Niels Lohmann </div> </div> <div class=md-social> <a href="https://github.com/nlohmann" target="_blank" rel="noopener" title="github.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 512 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><path d="M173.9 397.4c0 2-2.3 3.6-5.2 3.6-3.3.3-5.6-1.3-5.6-3.6 0-2 2.3-3.6 5.2-3.6 3-.3 5.6 1.3 5.6 3.6m-31.1-4.5c-.7 2 1.3 4.3 4.3 4.9 2.6 1 5.6 0 6.2-2s-1.3-4.3-4.3-5.2c-2.6-.7-5.5.3-6.2 2.3m44.2-1.7c-2.9.7-4.9 2.6-4.6 4.9.3 2 2.9 3.3 5.9 2.6 2.9-.7 4.9-2.6 4.6-4.6-.3-1.9-3-3.2-5.9-2.9M252.8 8C114.1 8 8 113.3 8 252c0 110.9 69.8 205.8 169.5 239.2 12.8 2.3 17.3-5.6 17.3-12.1 0-6.2-.3-40.4-.3-61.4 0 0-70 15-84.7-29.8 0 0-11.4-29.1-27.8-36.6 0 0-22.9-15.7 1.6-15.4 0 0 24.9 2 38.6 25.8 21.9 38.6 58.6 27.5 72.9 20.9 2.3-16 8.8-27.1 16-33.7-55.9-6.2-112.3-14.3-112.3-110.5 0-27.5 7.6-41.3 23.6-58.9-2.6-6.5-11.1-33.3 2.6-67.9 20.9-6.5 69 27 69 27 20-5.6 41.5-8.5 62.8-8.5s42.8 2.9 62.8 8.5c0 0 48.1-33.6 69-27 13.7 34.7 5.2 61.4 2.6 67.9 16 17.7 25.8 31.5 25.8 58.9 0 96.5-58.9 104.2-114.8 110.5 9.2 7.9 17 22.9 17 46.4 0 33.7-.3 75.4-.3 83.6 0 6.5 4.6 14.4 17.3 12.1C436.2 457.8 504 362.9 504 252 504 113.3 391.5 8 252.8 8M105.2 352.9c-1.3 1-1 3.3.7 5.2 1.6 1.6 3.9 2.3 5.2 1 1.3-1 1-3.3-.7-5.2-1.6-1.6-3.9-2.3-5.2-1m-10.8-8.1c-.7 1.3.3 2.9 2.3 3.9 1.6 1 3.6.7 4.3-.7.7-1.3-.3-2.9-2.3-3.9-2-.6-3.6-.3-4.3.7m32.4 35.6c-1.6 1.3-1 4.3 1.3 6.2 2.3 2.3 5.2 2.6 6.5 1 1.3-1.3.7-4.3-1.3-6.2-2.2-2.3-5.2-2.6-6.5-1m-11.4-14.7c-1.6 1-1.6 3.6 0 5.9s4.3 3.3 5.6 2.3c1.6-1.3 1.6-3.9 0-6.2-1.4-2.3-4-3.3-5.6-2"/></svg> </a> <a href="https://www.linkedin.com/in/nielslohmann/" target="_blank" rel="noopener" title="www.linkedin.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 448 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><path d="M416 32H31.9C14.3 32 0 46.5 0 64.3v383.4C0 465.5 14.3 480 31.9 480H416c17.6 0 32-14.5 32-32.3V64.3c0-17.8-14.4-32.3-32-32.3M135.4 416H69V202.2h66.5V416zM102.2 96a38.5 38.5 0 1 1 0 77 38.5 38.5 0 1 1 0-77m282.1 320h-66.4V312c0-24.8-.5-56.7-34.5-56.7-34.6 0-39.9 27-39.9 54.9V416h-66.4V202.2h63.7v29.2h.9c8.9-16.8 30.6-34.5 62.9-34.5 67.2 0 79.7 44.3 79.7 101.9z"/></svg> </a> <a href="https://www.xing.com/profile/Niels_Lohmann" target="_blank" rel="noopener" title="www.xing.com" class="md-social__link"> <svLine truncated
|
||||
</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">¶</a></h2> <ul> <li><a href=../is_discarded/ >is_discarded</a> - return whether the view is invalid</li> <li><a href=../../basic_json_document/root/ >root</a> - the view of a document's root value</li> <li><a href=../../view_mode/ >view_mode</a> - whether a document and its views can be edited</li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">¶</a></h2> <ul> <li>Added in version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="October 26, 2026 19:13:30 UTC">October 26, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright © 2013-2026 Niels Lohmann </div> </div> <div class=md-social> <a href="https://github.com/nlohmann" target="_blank" rel="noopener" title="github.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 512 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><path d="M173.9 397.4c0 2-2.3 3.6-5.2 3.6-3.3.3-5.6-1.3-5.6-3.6 0-2 2.3-3.6 5.2-3.6 3-.3 5.6 1.3 5.6 3.6m-31.1-4.5c-.7 2 1.3 4.3 4.3 4.9 2.6 1 5.6 0 6.2-2s-1.3-4.3-4.3-5.2c-2.6-.7-5.5.3-6.2 2.3m44.2-1.7c-2.9.7-4.9 2.6-4.6 4.9.3 2 2.9 3.3 5.9 2.6 2.9-.7 4.9-2.6 4.6-4.6-.3-1.9-3-3.2-5.9-2.9M252.8 8C114.1 8 8 113.3 8 252c0 110.9 69.8 205.8 169.5 239.2 12.8 2.3 17.3-5.6 17.3-12.1 0-6.2-.3-40.4-.3-61.4 0 0-70 15-84.7-29.8 0 0-11.4-29.1-27.8-36.6 0 0-22.9-15.7 1.6-15.4 0 0 24.9 2 38.6 25.8 21.9 38.6 58.6 27.5 72.9 20.9 2.3-16 8.8-27.1 16-33.7-55.9-6.2-112.3-14.3-112.3-110.5 0-27.5 7.6-41.3 23.6-58.9-2.6-6.5-11.1-33.3 2.6-67.9 20.9-6.5 69 27 69 27 20-5.6 41.5-8.5 62.8-8.5s42.8 2.9 62.8 8.5c0 0 48.1-33.6 69-27 13.7 34.7 5.2 61.4 2.6 67.9 16 17.7 25.8 31.5 25.8 58.9 0 96.5-58.9 104.2-114.8 110.5 9.2 7.9 17 22.9 17 46.4 0 33.7-.3 75.4-.3 83.6 0 6.5 4.6 14.4 17.3 12.1C436.2 457.8 504 362.9 504 252 504 113.3 391.5 8 252.8 8M105.2 352.9c-1.3 1-1 3.3.7 5.2 1.6 1.6 3.9 2.3 5.2 1 1.3-1 1-3.3-.7-5.2-1.6-1.6-3.9-2.3-5.2-1m-10.8-8.1c-.7 1.3.3 2.9 2.3 3.9 1.6 1 3.6.7 4.3-.7.7-1.3-.3-2.9-2.3-3.9-2-.6-3.6-.3-4.3.7m32.4 35.6c-1.6 1.3-1 4.3 1.3 6.2 2.3 2.3 5.2 2.6 6.5 1 1.3-1.3.7-4.3-1.3-6.2-2.2-2.3-5.2-2.6-6.5-1m-11.4-14.7c-1.6 1-1.6 3.6 0 5.9s4.3 3.3 5.6 2.3c1.6-1.3 1.6-3.9 0-6.2-1.4-2.3-4-3.3-5.6-2"/></svg> </a> <a href="https://www.linkedin.com/in/nielslohmann/" target="_blank" rel="noopener" title="www.linkedin.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 448 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><path d="M416 32H31.9C14.3 32 0 46.5 0 64.3v383.4C0 465.5 14.3 480 31.9 480H416c17.6 0 32-14.5 32-32.3V64.3c0-17.8-14.4-32.3-32-32.3M135.4 416H69V202.2h66.5V416zM102.2 96a38.5 38.5 0 1 1 0 77 38.5 38.5 0 1 1 0-77m282.1 320h-66.4V312c0-24.8-.5-56.7-34.5-56.7-34.6 0-39.9 27-39.9 54.9V416h-66.4V202.2h63.7v29.2h.9c8.9-16.8 30.6-34.5 62.9-34.5 67.2 0 79.7 44.3 79.7 101.9z"/></svg> </a> <a href="https://www.xing.com/profiLine truncated
|
||||
@@ -1,16 +1,25 @@
|
||||
# nlohmann::basic_json_view::basic_json_view
|
||||
|
||||
```
|
||||
// (1)
|
||||
basic_json_view() noexcept = default;
|
||||
|
||||
// (2) only for Mode == view_mode::editable
|
||||
basic_json_view(const basic_json_view<BasicJsonType, view_mode::read_only>& other) noexcept;
|
||||
```
|
||||
|
||||
Creates an invalid (discarded) view: [`type()`](https://json.nlohmann.me/api/basic_json_view/type/index.md) is `value_t::discarded` and [`is_discarded()`](https://json.nlohmann.me/api/basic_json_view/is_discarded/index.md) is `true`.
|
||||
1. Creates an invalid (discarded) view: [`type()`](https://json.nlohmann.me/api/basic_json_view/type/index.md) is `value_t::discarded` and [`is_discarded()`](https://json.nlohmann.me/api/basic_json_view/is_discarded/index.md) is `true`.
|
||||
1. Converts a view of a read-only document into a view of an editable document (implicitly), so that a function taking a [`json_editable_view`](https://json.nlohmann.me/api/json_editable_view/index.md) accepts both. The result is a view of the same value of the same read-only document. See [`view_mode`](https://json.nlohmann.me/api/view_mode/index.md) for why there is no conversion the other way.
|
||||
|
||||
This is the only constructor a caller can use directly. Every other view is obtained from a [`basic_json_document`](https://json.nlohmann.me/api/basic_json_document/index.md), via [`root()`](https://json.nlohmann.me/api/basic_json_document/root/index.md) or by navigating into a container with [`operator[]`](https://json.nlohmann.me/api/basic_json_view/operator%5B%5D/index.md), [`at`](https://json.nlohmann.me/api/basic_json_view/at/index.md), [`front`](https://json.nlohmann.me/api/basic_json_view/front/index.md), [`back`](https://json.nlohmann.me/api/basic_json_view/back/index.md), [`find`](https://json.nlohmann.me/api/basic_json_view/find/index.md), or iteration.
|
||||
## Parameters
|
||||
|
||||
`other` (in) : a view of a read-only document with the same `BasicJsonType`
|
||||
|
||||
Apart from these, a view is obtained from a [`basic_json_document`](https://json.nlohmann.me/api/basic_json_document/index.md), via [`root()`](https://json.nlohmann.me/api/basic_json_document/root/index.md) or by navigating into a container with [`operator[]`](https://json.nlohmann.me/api/basic_json_view/operator%5B%5D/index.md), [`at`](https://json.nlohmann.me/api/basic_json_view/at/index.md), [`front`](https://json.nlohmann.me/api/basic_json_view/front/index.md), [`back`](https://json.nlohmann.me/api/basic_json_view/back/index.md), [`find`](https://json.nlohmann.me/api/basic_json_view/find/index.md), or iteration.
|
||||
|
||||
## Exception safety
|
||||
|
||||
No-throw guarantee: this constructor never throws exceptions.
|
||||
No-throw guarantee: these constructors never throw exceptions.
|
||||
|
||||
## Complexity
|
||||
|
||||
@@ -57,6 +66,7 @@ true
|
||||
|
||||
- [is_discarded](https://json.nlohmann.me/api/basic_json_view/is_discarded/index.md) - return whether the view is invalid
|
||||
- [root](https://json.nlohmann.me/api/basic_json_document/root/index.md) - the view of a document's root value
|
||||
- [view_mode](https://json.nlohmann.me/api/view_mode/index.md) - whether a document and its views can be edited
|
||||
|
||||
## Version history
|
||||
|
||||
|
||||
@@ -47,7 +47,7 @@ the duplicates.
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -1,8 +1,8 @@
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/begin/" rel="canonical"><link href=../back/ rel=prev><link href=../cbegin/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>begin - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#nlohmannbasic_json_viewbegin class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> begin </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5"/></svg> </labeLine truncated
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/begin/" rel="canonical"><link href=../back/ rel=prev><link href=../cbegin/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>begin - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#nlohmannbasic_json_viewbegin class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> begin </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5"/></svg> </labeLine truncated
|
||||
</code></pre></div> <p>Returns an iterator to the first element of an array, or the first member value of an object, in <strong>document order</strong> -- the order the values appear in the source text, not sorted by key. A primitive value iterates as a range of one element (itself), and a <code class=highlight><span class=kc>null</span></code> value or a <a href=../is_discarded/ >discarded</a> view iterates as an empty range.</p> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">¶</a></h2> <p>Iterator to the first element.</p> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">¶</a></h2> <p>No-throw guarantee: this function never throws exceptions.</p> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">¶</a></h2> <p>Constant.</p> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">¶</a></h2> <p>For an object, iteration visits <strong>every</strong> member, including all occurrences of a duplicate key -- unlike <a href=../operator%5B%5D/ ><code>operator[]</code></a>, <a href=../at/ ><code>at</code></a>, <a href=../find/ ><code>find</code></a>, and <a href=../contains/ ><code>contains</code></a>, which all resolve to the <em>first</em> member with a given key. See the <a href=../operator%5B%5D/#notes>Notes on duplicate keys</a> of <code>operator[]</code>.</p> <p>Because objects are iterated in document order rather than sorted by key, the order seen here can differ from what iterating the <a href=../materialize/ ><code>materialize()</code></a>d <code>BasicJsonType</code> value would produce: a <code class=highlight><span class=n>basic_json</span></code> object (<code>std::map</code>-backed by default) sorts its keys, while a view does not.</p> <p>An <code>ordered_json</code> value also keeps document order, but it keeps only one entry per key: as <code>parse()</code> does, it keeps the <em>last</em> value, at the position of the key's <em>first</em> occurrence. The view, in contrast, visits every member, including the duplicates.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">¶</a></h2> <details class=example> <summary>Example</summary> <p>The example below iterates a log record's members with <code>begin()</code>/<a href=../end/ ><code>end()</code></a> and prints them in the order they were written. Materializing the record into a <code>BasicJsonType</code> object and iterating that would instead print the members sorted by key.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><iostream></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json_view.hpp></span>
|
||||
|
||||
<span class=k>using</span><span class=w> </span><span class=n>json_document</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
|
||||
<span class=kt>int</span><span class=w> </span><span class=nf>main</span><span class=p>()</span>
|
||||
<span class=p>{</span>
|
||||
|
||||
@@ -36,7 +36,7 @@ The example below iterates a log record's members with `begin()`/[`end()`](https
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -33,8 +33,8 @@ Constant.
|
||||
#include <numeric>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using json_view = nlohmann::json_view;
|
||||
using nlohmann::json_document;
|
||||
using nlohmann::json_view;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -1,10 +1,10 @@
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/cbegin/" rel="canonical"><link href=../begin/ rel=prev><link href=../cend/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>cbegin - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#nlohmannbasic_json_viewcbegin class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> cbegin </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5"/></svg> </lLine truncated
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/cbegin/" rel="canonical"><link href=../begin/ rel=prev><link href=../cend/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>cbegin - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#nlohmannbasic_json_viewcbegin class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> cbegin </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5"/></svg> </lLine truncated
|
||||
</code></pre></div> <p>Returns an iterator to the first element, in <a href=../begin/ >document order</a>. Equivalent to <a href=../begin/ ><code>begin()</code></a>: a view is always read-only, so <code class=highlight><span class=n>const_iterator</span></code> and <code class=highlight><span class=n>iterator</span></code> are the same type, and <code>cbegin()</code> exists only so that generic code that expects a <code>cbegin()</code>/<code>cend()</code> pair works with a view too.</p> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">¶</a></h2> <p>Iterator to the first element; identical to what <a href=../begin/ ><code>begin()</code></a> returns.</p> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">¶</a></h2> <p>No-throw guarantee: this function never throws exceptions.</p> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">¶</a></h2> <p>Constant.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">¶</a></h2> <details class=example> <summary>Example</summary> <p>The example below sums many measurements with <code>std::accumulate</code>, using <code>cbegin()</code>/<a href=../cend/ ><code>cend()</code></a> as the range -- the same way it would for any standard container -- without ever materializing the whole array into a <code>BasicJsonType</code> value.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><iostream></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><numeric></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json_view.hpp></span>
|
||||
|
||||
<span class=k>using</span><span class=w> </span><span class=n>json_document</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>json_view</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_view</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_view</span><span class=p>;</span>
|
||||
|
||||
<span class=kt>int</span><span class=w> </span><span class=nf>main</span><span class=p>()</span>
|
||||
<span class=p>{</span>
|
||||
|
||||
@@ -29,8 +29,8 @@ The example below sums many measurements with `std::accumulate`, using `cbegin()
|
||||
#include <numeric>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using json_view = nlohmann::json_view;
|
||||
using nlohmann::json_document;
|
||||
using nlohmann::json_view;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -33,8 +33,8 @@ Constant.
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using json_view = nlohmann::json_view;
|
||||
using nlohmann::json_document;
|
||||
using nlohmann::json_view;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -1,10 +1,10 @@
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/cend/" rel="canonical"><link href=../cbegin/ rel=prev><link href=../contains/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>cend - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#nlohmannbasic_json_viewcend class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> cend </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" 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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/cend/" rel="canonical"><link href=../cbegin/ rel=prev><link href=../contains/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>cend - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> cend </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" 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12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5"/></svg> </labeLine truncated
|
||||
</code></pre></div> <p>Returns an iterator to one past the last element, in <a href=../begin/ >document order</a>. Equivalent to <a href=../end/ ><code>end()</code></a>: a view is always read-only, so <code class=highlight><span class=n>const_iterator</span></code> and <code class=highlight><span class=n>iterator</span></code> are the same type, and <code>cend()</code> exists only so that generic code that expects a <code>cbegin()</code>/<code>cend()</code> pair works with a view too.</p> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">¶</a></h2> <p>Iterator one past the last element; identical to what <a href=../end/ ><code>end()</code></a> returns.</p> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">¶</a></h2> <p>No-throw guarantee: this function never throws exceptions.</p> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">¶</a></h2> <p>Constant.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">¶</a></h2> <details class=example> <summary>Example</summary> <p>The example below checks that every record of a batch is an object with <code>std::all_of</code>, using <a href=../cbegin/ ><code>cbegin()</code></a>/<code>cend()</code> as the range -- the same way it would for any standard container -- before materializing any record of the batch.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><algorithm></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><iostream></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json_view.hpp></span>
|
||||
|
||||
<span class=k>using</span><span class=w> </span><span class=n>json_document</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>json_view</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_view</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_view</span><span class=p>;</span>
|
||||
|
||||
<span class=kt>int</span><span class=w> </span><span class=nf>main</span><span class=p>()</span>
|
||||
<span class=p>{</span>
|
||||
|
||||
@@ -29,8 +29,8 @@ The example below checks that every record of a batch is an object with `std::al
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using json_view = nlohmann::json_view;
|
||||
using nlohmann::json_document;
|
||||
using nlohmann::json_view;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -78,7 +78,7 @@ view.
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
@@ -124,7 +124,7 @@ view.
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
using json_pointer = nlohmann::json::json_pointer;
|
||||
|
||||
int main()
|
||||
|
||||
@@ -1,4 +1,4 @@
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/contains/" rel="canonical"><link href=../cend/ rel=prev><link href=../count/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>contains - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> contains </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5"/></Line truncated
|
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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/contains/" rel="canonical"><link href=../cend/ rel=prev><link href=../count/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>contains - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#nlohmannbasic_json_viewcontains class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> contains </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark 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4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5"/></Line truncated
|
||||
<span class=kt>bool</span><span class=w> </span><span class=nf>contains</span><span class=p>(</span><span class=n>string_view_t</span><span class=w> </span><span class=n>key</span><span class=p>)</span><span class=w> </span><span class=k>const</span><span class=p>;</span>
|
||||
<span class=kt>bool</span><span class=w> </span><span class=nf>contains</span><span class=p>(</span><span class=k>const</span><span class=w> </span><span class=kt>char</span><span class=o>*</span><span class=w> </span><span class=n>key</span><span class=p>)</span><span class=w> </span><span class=k>const</span><span class=p>;</span>
|
||||
<span class=kt>bool</span><span class=w> </span><span class=nf>contains</span><span class=p>(</span><span class=k>const</span><span class=w> </span><span class=n>string_t</span><span class=o>&</span><span class=w> </span><span class=n>key</span><span class=p>)</span><span class=w> </span><span class=k>const</span><span class=p>;</span>
|
||||
@@ -8,7 +8,7 @@
|
||||
</code></pre></div> <ol> <li>Checks whether the value is an object with a member with key <code>key</code>.</li> <li>Checks whether a <abbr title="JavaScript Object Notation">JSON</abbr> pointer <code>ptr</code> can be resolved, starting at this value.</li> </ol> <h2 id=parameters>Parameters<a class=headerlink href=#parameters title="Permanent link">¶</a></h2> <dl> <dt><code>key</code> (in)</dt> <dd>key value to check its existence</dd> <dt><code>ptr</code> (in)</dt> <dd><abbr title="JavaScript Object Notation">JSON</abbr> pointer to check its existence</dd> </dl> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">¶</a></h2> <ol> <li><code class=highlight><span class=nb>true</span></code> if the value is an object and has a member with key <code>key</code>, <code class=highlight><span class=nb>false</span></code> otherwise</li> <li><code class=highlight><span class=nb>true</span></code> if <code>ptr</code> can be resolved to a value starting at this view, <code class=highlight><span class=nb>false</span></code> otherwise</li> </ol> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">¶</a></h2> <p>No-throw guarantee: this function never throws exceptions.</p> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">¶</a></h2> <ol> <li>Linear in the number of members: as for <a href=../../ordered_json/ ><code>ordered_json</code></a>, members are compared one after another, in document order, stopping at the first match. Each comparison first checks the key's length -- already known from the index, without reading the key bytes -- before comparing its content. Objects with 128 or more members get a hash index of their keys while parsing, so that a lookup in them takes constant time on average.</li> <li>Linear in the number of reference tokens of <code>ptr</code> and, for each token, in the number of members of the object at that level or the index into the array -- as for <a href=../operator%5B%5D/#complexity><code>operator[]</code></a> and <a href=../at/#complexity><code>at</code></a> with a <abbr title="JavaScript Object Notation">JSON</abbr> pointer.</li> </ol> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">¶</a></h2> <div class="admonition warning"> <p class=admonition-title>Duplicate keys: the first member wins</p> <p>If the source text repeats a key, this resolves to the <em>first</em> member with it, not to the last one that <a href=../materialize/ ><code>materialize()</code></a> and <code>parse()</code> keep. See the <a href=../operator%5B%5D/#notes>Notes on duplicate keys</a> of <code>operator[]</code> and <a href=../../../features/json_view/#duplicate-keys>Duplicate keys</a> for the reasons and for how to get the last value.</p> </div> <p>Overload 1 always returns <code class=highlight><span class=nb>false</span></code> when the value is not an object -- including a <a href=../is_discarded/ >discarded</a> view.</p> <div class="admonition info"> <p class=admonition-title>Postconditions</p> <p>If <code class=highlight><span class=n>v</span><span class=p>.</span><span class=n>contains</span><span class=p>(</span><span class=n>key</span><span class=p>)</span></code> returns <code class=highlight><span class=nb>true</span></code>, then <code class=highlight><span class=n>v</span><span class=p>[</span><span class=n>key</span><span class=p>]</span></code> is not <a href=../is_discarded/ >discarded</a> and <code class=highlight><span class=n>v</span><span class=p>.</span><span class=n>at</span><span class=p>(</span><span class=n>key</span><span class=p>)</span></code> does not throw. If <code class=highlight><span class=n>v</span><span class=p>.</span><span class=n>contains</span><span class=p>(</span><span class=n>ptr</span><span class=p>)</span></code> returns <code class=highlight><span class=nb>true</span></code>, then <code class=highlight><span class=n>v</span><span class=p>[</span><span class=n>ptr</span><span class=p>]</span></code> is not discarded and <code class=highlight><span class=n>v</span><span class=p>.</span><span class=n>at</span><span class=p>(</span><span class=n>ptr</span><span class=p>)</span></code> does not throw.</p> </div> <div class="admonition info"> <p class=admonition-title>Overload 2 never throws</p> <p>Unlike <a href=../../basic_json/contains/ ><code>BasicJsonType::contains(const json_pointer&)</code></a>, which can throw for certain malformed pointers (for instance an empty array-index reference token), overload 2 never throws: a missing key, an out-of-range or malformed array index, a <code class=highlight><span class=s>"-"</span></code> index, or a reference token used on a primitive all simply make it return <code class=highlight><span class=nb>false</span></code>.</p> </div> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">¶</a></h2> <details class=examLine truncated
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json_view.hpp></span>
|
||||
|
||||
<span class=k>using</span><span class=w> </span><span class=n>json_document</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
|
||||
<span class=kt>int</span><span class=w> </span><span class=nf>main</span><span class=p>()</span>
|
||||
<span class=p>{</span>
|
||||
@@ -39,7 +39,7 @@
|
||||
</code></pre></div> </details> <details class=example> <summary>Example: (2) check with <abbr title="JavaScript Object Notation">JSON</abbr> pointer</summary> <p>The example below checks an optional, nested field with a <abbr title="JavaScript Object Notation">JSON</abbr> pointer, and shows two pointers that <code class=highlight><span class=n>contains</span><span class=p>()</span></code> resolves to <code class=highlight><span class=nb>false</span></code> without throwing.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><iostream></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json_view.hpp></span>
|
||||
|
||||
<span class=k>using</span><span class=w> </span><span class=n>json_document</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>json_pointer</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json</span><span class=o>::</span><span class=n>json_pointer</span><span class=p>;</span>
|
||||
|
||||
<span class=kt>int</span><span class=w> </span><span class=nf>main</span><span class=p>()</span>
|
||||
|
||||
@@ -59,7 +59,7 @@ The example below counts how many of a batch of records carry an optional `retry
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
@@ -102,7 +102,7 @@ The example below checks an optional, nested field with a JSON pointer, and show
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
using json_pointer = nlohmann::json::json_pointer;
|
||||
|
||||
int main()
|
||||
|
||||
@@ -54,7 +54,7 @@ If the source text repeats a key, `count()` returns more than `#!cpp 1` for it,
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -1,10 +1,10 @@
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/count/" rel="canonical"><link href=../contains/ rel=prev><link href=../dump/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>count - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> count </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5"/></svg> </laLine truncated
|
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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/count/" rel="canonical"><link href=../contains/ rel=prev><link href=../dump/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>count - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#nlohmannbasic_json_viewcount class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> count </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5"/></svg> </laLine truncated
|
||||
<span class=n>size_type</span><span class=w> </span><span class=nf>count</span><span class=p>(</span><span class=k>const</span><span class=w> </span><span class=kt>char</span><span class=o>*</span><span class=w> </span><span class=n>key</span><span class=p>)</span><span class=w> </span><span class=k>const</span><span class=p>;</span>
|
||||
<span class=n>size_type</span><span class=w> </span><span class=nf>count</span><span class=p>(</span><span class=k>const</span><span class=w> </span><span class=n>string_t</span><span class=o>&</span><span class=w> </span><span class=n>key</span><span class=p>)</span><span class=w> </span><span class=k>const</span><span class=p>;</span>
|
||||
</code></pre></div> <p>Returns the number of members with key <code>key</code> if the value is an object, <code class=highlight><span class=mi>0</span></code> otherwise. Members with a repeated key are all counted.</p> <h2 id=parameters>Parameters<a class=headerlink href=#parameters title="Permanent link">¶</a></h2> <dl> <dt><code>key</code> (in)</dt> <dd>key value of the element to count</dd> </dl> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">¶</a></h2> <p>the number of members of the object with key <code>key</code> (duplicates included), or <code class=highlight><span class=mi>0</span></code> if the value is not an object or has no such member.</p> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">¶</a></h2> <p>No-throw guarantee: this function never throws exceptions.</p> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">¶</a></h2> <p>Linear in the number of members: unlike the lookup functions, <code>count()</code> does not stop at the first match, because it has to count every member with the key. Members are compared one after another, in document order. Each comparison first checks the key's length -- already known from the index, without reading the key bytes -- before comparing its content. The hash index of the keys of objects with 128 or more members does not help here, since every member is visited.</p> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">¶</a></h2> <p>This method always returns <code class=highlight><span class=mi>0</span></code> when the value is not an object -- including a <a href=../is_discarded/ >discarded</a> view.</p> <p>If the source text repeats a key, <code>count()</code> returns more than <code class=highlight><span class=mi>1</span></code> for it, even though the <a href=../materialize/ >materialized</a> value (like the result of <code>parse()</code>) would have only one member with that key. Hence <code class=highlight><span class=n>count</span><span class=p>(</span><span class=n>key</span><span class=p>)</span><span class=w> </span><span class=o>></span><span class=w> </span><span class=mi>1</span></code> detects duplicate keys. This is unlike the lookup functions (<a href=../operator%5B%5D/ ><code>operator[]</code></a>, <a href=../at/ ><code>at</code></a>, <a href=../find/ ><code>find</code></a>, <a href=../contains/ ><code>contains</code></a>), which resolve to the <em>first</em> member; see the <a href=../operator%5B%5D/#notes>Notes on duplicate keys</a> of <code>operator[]</code>.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">¶</a></h2> <details class=example> <summary>Example</summary> <p>The example below validates that every transaction of a batch carries exactly one <code>amount</code> field, using <code>count()</code> before deciding whether to materialize a transaction at all. It reports a transaction with no <code>amount</code> field and one with a duplicated <code>amount</code> field.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><iostream></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json_view.hpp></span>
|
||||
|
||||
<span class=k>using</span><span class=w> </span><span class=n>json_document</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
|
||||
<span class=kt>int</span><span class=w> </span><span class=nf>main</span><span class=p>()</span>
|
||||
<span class=p>{</span>
|
||||
|
||||
@@ -40,7 +40,7 @@ The example below validates that every transaction of a batch carries exactly on
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -86,8 +86,8 @@ parsing already reduces every number to its parsed value.
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using json_view = nlohmann::json_view;
|
||||
using nlohmann::json_document;
|
||||
using nlohmann::json_view;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -1,12 +1,12 @@
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/dump/" rel="canonical"><link href=../count/ rel=prev><link href=../empty/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>dump - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#nlohmannbasic_json_viewdump class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> dump </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5"/></svg> </label> <Line truncated
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/dump/" rel="canonical"><link href=../count/ rel=prev><link href=../empty/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>dump - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#nlohmannbasic_json_viewdump class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> dump </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5"/></svg> </label> <Line truncated
|
||||
<span class=w> </span><span class=k>const</span><span class=w> </span><span class=kt>char</span><span class=w> </span><span class=n>indent_char</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=sc>' '</span><span class=p>,</span>
|
||||
<span class=w> </span><span class=k>const</span><span class=w> </span><span class=kt>bool</span><span class=w> </span><span class=n>ensure_ascii</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=nb>false</span><span class=p>,</span>
|
||||
<span class=w> </span><span class=k>const</span><span class=w> </span><span class=n>number_format</span><span class=w> </span><span class=n>numbers</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>number_format</span><span class=o>::</span><span class=n>shortest</span><span class=p>)</span><span class=w> </span><span class=k>const</span><span class=p>;</span>
|
||||
</code></pre></div> <p>Serializes this value (and its subtree) directly from the flat index, without ever building a <code>BasicJsonType</code> value first. With the default <code class=highlight><span class=n>numbers</span><span class=w> </span><span class=o>==</span><span class=w> </span><span class=n>number_format</span><span class=o>::</span><span class=n>shortest</span></code>, the result is the same string <a href=../../basic_json/dump/ ><code>BasicJsonType::dump</code></a> would produce for the value <a href=../../basic_json/parse/ ><code>BasicJsonType::parse()</code></a> builds from the same source text, called with the same <code>indent</code>, <code>indent_char</code>, and <code>ensure_ascii</code> -- except that members of an object appear in document order rather than sorted by key, and <em>every</em> occurrence of a repeated key is written rather than only the last one (see <a href=../operator%5B%5D/#notes>Notes on duplicate keys</a>). For a <code>json_view</code> (whose <code>BasicJsonType</code> is not ordered), this means <code>dump()</code> can print an object's members in a different order than <a href=../materialize/ ><code>materialize()</code></a><code>.dump()</code> of the same subtree.</p> <h2 id=parameters>Parameters<a class=headerlink href=#parameters title="Permanent link">¶</a></h2> <dl> <dt><code>indent</code> (in)</dt> <dd>If <code>indent</code> is nonnegative, array elements and object members are pretty-printed with that indent level. An indent level of <code>0</code> only inserts newlines. <code>-1</code> (the default) selects the most compact representation.</dd> <dt><code>indent_char</code> (in)</dt> <dd>The character used for indentation if <code>indent</code> is greater than <code>0</code>. The default is <code></code> (space).</dd> <dt><code>ensure_ascii</code> (in)</dt> <dd>If <code>ensure_ascii</code> is <code class=highlight><span class=nb>true</span></code>, all non-<abbr title="American Standard Code for Information Interchange">ASCII</abbr> characters in the output are escaped with <code>\uXXXX</code> sequences, and the result consists of <abbr title="American Standard Code for Information Interchange">ASCII</abbr> characters only.</dd> <dt><code>numbers</code> (in)</dt> <dd>how to write numbers, see <a href=../number_format/ ><code>number_format</code></a>: <code>shortest</code> (the default) writes them the way <a href=../../basic_json/dump/ ><code>BasicJsonType::dump</code></a> would; <code>source</code> copies every number exactly as it appears in the source text.</dd> </dl> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">¶</a></h2> <p>string containing the serialization of this value, or <code class=highlight><span class=s>"<discarded>"</span></code> if the view is <a href=../is_discarded/ >discarded</a>.</p> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">¶</a></h2> <p>Strong exception safety: if an exception is thrown, there are no changes to the view or the document it refers to.</p> <h2 id=exceptions>Exceptions<a class=headerlink href=#exceptions title="Permanent link">¶</a></h2> <p>May throw <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>bad_alloc</span></code> if allocating the output string fails. Unlike <a href=../../basic_json/dump/ ><code>BasicJsonType::dump</code></a>, there is no <code>error_handler</code> parameter and no <a href=../../../home/exceptions/#jsonexceptiontype_error316><code>type_error.316</code></a>: the view only ever holds text the parser already validated as <abbr title="Unicode Transformation Format">UTF</abbr>-8, so there is nothing to replace or ignore.</p> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">¶</a></h2> <p>Linear in the size of the output text.</p> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">¶</a></h2> <p>The walk over the subtree is iterative, so the nesting depth it can write is limited by available memory only, not by the call stack -- as for <a href=../materialize/ ><code>materialize()</code></a>.</p> <p>Strings are escaped by the same rules as <a href=../../basic_json/dump/ ><code>BasicJsonType::dump</code></a>.</p> <p>With <code class=highlight><span class=n>numbers</span><span class=w> </span><span class=o>==</span><span class=w> </span><span class=n>number_format</span><span class=o>::</span><span class=n>shortest</span></code>, floats are written with the library's shortest round-trip conversion, exactly as <a href=../../basic_json/dump/ ><code>BasicJsonType::dump</code></a> would (e.g. <code class=highlight><span class=mf>1.5</span></code>, <code class=highlight><span class=mf>100.0</span></code>, <code class=highlight><span class=mf>1e+100</span></code>), and integers are copied from the source text -- already canonical in <abbr title="JavaScript Object Notation">JLine truncated
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json_view.hpp></span>
|
||||
|
||||
<span class=k>using</span><span class=w> </span><span class=n>json_document</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>json_view</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_view</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_view</span><span class=p>;</span>
|
||||
|
||||
<span class=kt>int</span><span class=w> </span><span class=nf>main</span><span class=p>()</span>
|
||||
<span class=p>{</span>
|
||||
|
||||
@@ -55,8 +55,8 @@ The example below forwards a single record out of a larger batch, and re-seriali
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using json_view = nlohmann::json_view;
|
||||
using nlohmann::json_document;
|
||||
using nlohmann::json_view;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -45,7 +45,7 @@ is `#!cpp false` for any string, regardless of its length.
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -1,8 +1,8 @@
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/empty/" rel="canonical"><link href=../dump/ rel=prev><link href=../end/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>empty - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#nlohmannbasic_json_viewempty class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> empty </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5"/></svg> </label> Line truncated
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/empty/" rel="canonical"><link href=../dump/ rel=prev><link href=../end/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>empty - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#nlohmannbasic_json_viewempty class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> empty </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5"/></svg> </label> Line truncated
|
||||
</code></pre></div> <p>Checks whether <a href=../size/ ><code>size()</code></a> is <code>0</code>, as <a href=../../basic_json/empty/ ><code>BasicJsonType::empty()</code></a> would for the same value.</p> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">¶</a></h2> <p>The return value depends on the type and is defined as follows:</p> <table> <thead> <tr> <th>Value type</th> <th>return value</th> </tr> </thead> <tbody> <tr> <td>null</td> <td><code class=highlight><span class=nb>true</span></code></td> </tr> <tr> <td>discarded</td> <td><code class=highlight><span class=nb>true</span></code></td> </tr> <tr> <td>boolean</td> <td><code class=highlight><span class=nb>false</span></code></td> </tr> <tr> <td>string</td> <td><code class=highlight><span class=nb>false</span></code></td> </tr> <tr> <td>number</td> <td><code class=highlight><span class=nb>false</span></code></td> </tr> <tr> <td>object</td> <td><code class=highlight><span class=n>object_t</span><span class=o>::</span><span class=n>empty</span><span class=p>()</span></code></td> </tr> <tr> <td>array</td> <td><code class=highlight><span class=n>array_t</span><span class=o>::</span><span class=n>empty</span><span class=p>()</span></code></td> </tr> </tbody> </table> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">¶</a></h2> <p>No-throw guarantee: this function never throws exceptions.</p> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">¶</a></h2> <p>Constant.</p> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">¶</a></h2> <p>As for <a href=../../basic_json/empty/ ><code>BasicJsonType::empty()</code></a>, this does not return whether a string value is empty -- it is <code class=highlight><span class=nb>false</span></code> for any string, regardless of its length.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">¶</a></h2> <details class=example> <summary>Example</summary> <p>The example below uses <a href=../size/ ><code>size()</code></a> and <code>empty()</code> to decide whether a parsed message is worth acting on, without materializing it into a <code>BasicJsonType</code> value.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><iostream></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json_view.hpp></span>
|
||||
|
||||
<span class=k>using</span><span class=w> </span><span class=n>json_document</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
|
||||
<span class=kt>int</span><span class=w> </span><span class=nf>main</span><span class=p>()</span>
|
||||
<span class=p>{</span>
|
||||
|
||||
@@ -42,7 +42,7 @@ The example below uses [`size()`](https://json.nlohmann.me/api/basic_json_view/s
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -36,7 +36,7 @@ way to reach the last element by stepping back from `end()`. Use [`back()`](back
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -1,8 +1,8 @@
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/end/" rel="canonical"><link href=../empty/ rel=prev><link href=../find/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>end - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/end/" rel="canonical"><link href=../empty/ rel=prev><link href=../find/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>end - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> end </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" 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</code></pre></div> <p>Returns an iterator to one past the last element of an array, one past the last member value of an object, in <strong>document order</strong> -- see <a href=../begin/ ><code>begin()</code></a>. A primitive value iterates as a range of one element (itself), and a <code class=highlight><span class=kc>null</span></code> value or a <a href=../is_discarded/ >discarded</a> view iterates as an empty range (<code class=highlight><span class=n>begin</span><span class=p>()</span><span class=w> </span><span class=o>==</span><span class=w> </span><span class=n>end</span><span class=p>()</span></code>).</p> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">¶</a></h2> <p>Iterator one past the last element.</p> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">¶</a></h2> <p>No-throw guarantee: this function never throws exceptions.</p> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">¶</a></h2> <p>Constant.</p> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">¶</a></h2> <p><code class=highlight><span class=n>iterator</span></code> is a forward iterator: unlike <code>BasicJsonType::iterator</code>, it cannot be decremented, so there is no way to reach the last element by stepping back from <code>end()</code>. Use <a href=../back/ ><code>back()</code></a> instead.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">¶</a></h2> <details class=example> <summary>Example</summary> <p>The example below scans a (possibly large) array of readings for the first one over a threshold, stopping the loop at <code>end()</code> as soon as one is found. Only the matching reading, if any, is ever materialized.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><iostream></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json_view.hpp></span>
|
||||
|
||||
<span class=k>using</span><span class=w> </span><span class=n>json_document</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
|
||||
<span class=kt>int</span><span class=w> </span><span class=nf>main</span><span class=p>()</span>
|
||||
<span class=p>{</span>
|
||||
|
||||
@@ -32,7 +32,7 @@ The example below scans a (possibly large) array of readings for the first one o
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -55,7 +55,7 @@ also does so for a [discarded](is_discarded.md) view -- there is no separate "in
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -1,10 +1,10 @@
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/find/" rel="canonical"><link href=../end/ rel=prev><link href=../front/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>find - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> find </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" 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12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5"/></svg> </label> <diLine truncated
|
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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/find/" rel="canonical"><link href=../end/ rel=prev><link href=../front/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>find - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#nlohmannbasic_json_viewfind class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> find </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" 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12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5"/></svg> </label> <diLine truncated
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<span class=n>iterator</span><span class=w> </span><span class=nf>find</span><span class=p>(</span><span class=k>const</span><span class=w> </span><span class=kt>char</span><span class=o>*</span><span class=w> </span><span class=n>key</span><span class=p>)</span><span class=w> </span><span class=k>const</span><span class=p>;</span>
|
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<span class=n>iterator</span><span class=w> </span><span class=nf>find</span><span class=p>(</span><span class=k>const</span><span class=w> </span><span class=n>string_t</span><span class=o>&</span><span class=w> </span><span class=n>key</span><span class=p>)</span><span class=w> </span><span class=k>const</span><span class=p>;</span>
|
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</code></pre></div> <p>Finds a member with key <code>key</code> -- the first one, should the key occur more than once (see <a href=../operator%5B%5D/#notes>Notes on duplicate keys</a>). If the value is not an object, or no member has this key, <a href=../end/ ><code>end()</code></a> is returned.</p> <h2 id=parameters>Parameters<a class=headerlink href=#parameters title="Permanent link">¶</a></h2> <dl> <dt><code>key</code> (in)</dt> <dd>key value of the element to search for</dd> </dl> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">¶</a></h2> <p>An iterator to the member with key <code>key</code>, or <a href=../end/ ><code>end()</code></a> if there is none or the value is not an object.</p> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">¶</a></h2> <p>No-throw guarantee: this function never throws exceptions.</p> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">¶</a></h2> <p>Linear in the number of members: as for <a href=../../ordered_json/ ><code>ordered_json</code></a>, members are compared one after another, in document order, stopping at the first match. Each comparison first checks the key's length -- already known from the index, without reading the key bytes -- before comparing its content. Objects with 128 or more members get a hash index of their keys while parsing, so that a lookup in them takes constant time on average.</p> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">¶</a></h2> <div class="admonition warning"> <p class=admonition-title>Duplicate keys: the first member wins</p> <p>If the source text repeats a key, this resolves to the <em>first</em> member with it, not to the last one that <a href=../materialize/ ><code>materialize()</code></a> and <code>parse()</code> keep. See the <a href=../operator%5B%5D/#notes>Notes on duplicate keys</a> of <code>operator[]</code> and <a href=../../../features/json_view/#duplicate-keys>Duplicate keys</a> for the reasons and for how to get the last value.</p> </div> <p>Unlike <a href=../../basic_json/find/ ><code>BasicJsonType::find</code></a>, which always returns <code class=highlight><span class=n>end</span><span class=p>()</span></code> for a non-object type, this also does so for a <a href=../is_discarded/ >discarded</a> view -- there is no separate "invalid" iterator to return.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">¶</a></h2> <details class=example> <summary>Example</summary> <p>The example below scans a batch of events for those that carry an optional <code>user_id</code> field, using <code>find()</code> instead of <a href=../operator%5B%5D/ ><code>operator[]</code></a> (which would throw for the events that are not objects at all) or <a href=../contains/ ><code>contains()</code></a> followed by a second lookup. Events without a match are never materialized.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><iostream></span>
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<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json_view.hpp></span>
|
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<span class=k>using</span><span class=w> </span><span class=n>json_document</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
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<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
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<span class=kt>int</span><span class=w> </span><span class=nf>main</span><span class=p>()</span>
|
||||
<span class=p>{</span>
|
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|
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@@ -42,7 +42,7 @@ The example below scans a batch of events for those that carry an optional `user
|
||||
#include <iostream>
|
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#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -45,7 +45,7 @@ view.
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
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|
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using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
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|
||||
int main()
|
||||
{
|
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@@ -1,8 +1,8 @@
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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/front/" rel="canonical"><link href=../find/ rel=prev><link href=../get/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>front - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/front/" rel="canonical"><link href=../find/ rel=prev><link href=../get/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>front - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> front </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" 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12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 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|
||||
</code></pre></div> <p>Returns the first element of an array, the first member value of an object, or the value itself if it is primitive (as for <a href=../../basic_json/front/ ><code>BasicJsonType::front()</code></a>, a primitive value is a range of one element).</p> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">¶</a></h2> <p>The first element or member value. For a primitive value (number, string, boolean), the value itself.</p> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">¶</a></h2> <p>Strong guarantee: there are no changes to the view or the document it refers to.</p> <h2 id=exceptions>Exceptions<a class=headerlink href=#exceptions title="Permanent link">¶</a></h2> <p>Throws <a href=../../../home/exceptions/#jsonexceptioninvalid_iterator214><code>invalid_iterator.214</code></a> if the view is <a href=../is_null/ >null</a> or <a href=../is_discarded/ >discarded</a>, or if it is an empty array or object.</p> <p>This exception does not carry a <a href=../../macros/json_diagnostics/ ><code>JSON_DIAGNOSTICS</code></a> path: the view has no <code>BasicJsonType</code> value to point at, so the exception is created without one, even if <code>BasicJsonType</code> was built with <code>JSON_DIAGNOSTICS</code> enabled.</p> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">¶</a></h2> <p>Constant.</p> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">¶</a></h2> <p>Unlike <a href=../../basic_json/front/ ><code>BasicJsonType::front()</code></a>, which has undefined behavior for an empty array or object, <code>front()</code> throws <code>invalid_iterator.214</code> for an empty array, an empty object, a null value, or a discarded view.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">¶</a></h2> <details class=example> <summary>Example</summary> <p>The example below reads only the earliest entry of a build log with <code>front()</code>, without materializing the rest of the (possibly long) log.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><iostream></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json_view.hpp></span>
|
||||
|
||||
<span class=k>using</span><span class=w> </span><span class=n>json_document</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
|
||||
<span class=kt>int</span><span class=w> </span><span class=nf>main</span><span class=p>()</span>
|
||||
<span class=p>{</span>
|
||||
|
||||
@@ -38,7 +38,7 @@ The example below reads only the earliest entry of a build log with `front()`, w
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
+39
-14
@@ -19,16 +19,36 @@ For the types below, the conversion works directly on the flat index -- no `Basi
|
||||
document's own buffer of decoded strings (see [`get_string()`](get_string.md))
|
||||
- `BasicJsonType` -- equivalent to [`materialize()`](materialize.md)
|
||||
- `basic_json_view` -- returns `#!cpp *this`
|
||||
- `#!cpp std::vector<U, A>` -- from an array, element by element, each converted with `#!cpp get<U>()`; `#!cpp
|
||||
std::vector<basic_json_view>` keeps a view of every element instead of a value
|
||||
- `#!cpp std::map<K, V, C, A>` and `#!cpp std::unordered_map<K, V, H, E, A>`, if `K` is constructible from a `#!cpp
|
||||
(const char*, std::size_t)` pair -- from an object, member by member, each value converted with `#!cpp get<V>()`; with a repeated
|
||||
key, the *last* value is kept, as [`BasicJsonType::parse()`](../basic_json/parse.md) (and
|
||||
[`materialize()`](materialize.md)) does; `#!cpp std::map<std::string, basic_json_view>` keeps views of the members
|
||||
instead of values
|
||||
- `#!cpp std::vector<U, A>` of the types above -- from an array, element by element, each converted with
|
||||
`#!cpp get<U>()`; `#!cpp std::vector<basic_json_view>` keeps a view of every element instead of a value
|
||||
- `#!cpp std::map<K, basic_json_view, C, A>` and `#!cpp std::unordered_map<K, basic_json_view, H, E, A>`, if `K` is
|
||||
constructible from a `#!cpp (const char*, std::size_t)` pair -- views of the members of an object; with a repeated
|
||||
key, the view of the *last* member is kept, as [`BasicJsonType::parse()`](../basic_json/parse.md) keeps its value
|
||||
|
||||
Every other `T` -- `#!cpp std::list`, `#!cpp std::pair`, `#!cpp std::array`, enumerations, user types with a
|
||||
`from_json()`, ... -- is converted by `#!cpp materialize().get<T>()`: the subtree is built into a real `BasicJsonType`
|
||||
A default-constructible `T` whose `from_json()` accepts views reads the view directly as well, without building a
|
||||
`BasicJsonType` value. This covers the library's own conversions of the standard library types -- all other
|
||||
`#!cpp std::vector`s, `#!cpp std::map`/`#!cpp std::unordered_map` (also with other key types), `#!cpp std::list`,
|
||||
`#!cpp std::deque`, `#!cpp std::set`, `#!cpp std::forward_list`, `#!cpp std::valarray`, `#!cpp std::array`, C arrays,
|
||||
`#!cpp std::pair`, `#!cpp std::tuple`, `#!cpp std::optional`, enumerations, `#!cpp std::filesystem::path`, ... --
|
||||
which give the same values as `#!cpp materialize().get<T>()` (from an object, a repeated key keeps the *last* value,
|
||||
as [`BasicJsonType::parse()`](../basic_json/parse.md) does), as well as the types of the
|
||||
[`NLOHMANN_DEFINE_TYPE_*`](../macros/nlohmann_define_type_intrusive.md) and
|
||||
[`NLOHMANN_DEFINE_DERIVED_TYPE_*`](../macros/nlohmann_define_derived_type.md) macros and the enumerations of
|
||||
[`NLOHMANN_JSON_SERIALIZE_ENUM`](../macros/nlohmann_json_serialize_enum.md), and any `from_json()` constrained to
|
||||
accept views, e.g. with [`is_json_view`](../is_json_view.md). A `from_json()` that also accepts types that are no JSON
|
||||
values at all, such as the unconstrained `#!cpp template<typename BasicJsonType> void from_json(const BasicJsonType&,
|
||||
T&)` of [arbitrary type conversions](../../features/arbitrary_types.md), is not called with a view: it may use
|
||||
`BasicJsonType` functions a view does not have. See [Writing generic code](../../features/json_view.md#writing-generic-code).
|
||||
|
||||
!!! warning "Duplicate keys"
|
||||
|
||||
Such a `from_json()` looks members up in the view, where a repeated key finds the **first** member, while
|
||||
`#!cpp materialize().get<T>()` sees the **last** one, as [`BasicJsonType::parse()`](../basic_json/parse.md)
|
||||
keeps it: for `#!cpp {"x":1,"x":2}`, `#!cpp get<point>()` reads `#!cpp x == 1`. See
|
||||
[Duplicate keys](../../features/json_view.md#duplicate-keys).
|
||||
|
||||
Every other `T` -- user types whose `from_json()` is written for `BasicJsonType` only, types without a default
|
||||
constructor, `#!cpp std::tuple`s holding references, ... -- is converted by `#!cpp materialize().get<T>()`: the subtree is built into a real `BasicJsonType`
|
||||
value first (as [`BasicJsonType::parse()`](../basic_json/parse.md) would), and converted from there exactly as
|
||||
[`BasicJsonType::get<T>()`](../basic_json/get.md) would convert it.
|
||||
|
||||
@@ -53,12 +73,15 @@ Strong guarantee: there are no changes to the view or the document it refers to.
|
||||
throws for the same JSON type and `T`.
|
||||
- For `#!cpp std::vector<U, A>`: throws `type_error.302` if the value is not an array; otherwise, whatever converting
|
||||
an element to `U` throws.
|
||||
- For `#!cpp std::map`/`#!cpp std::unordered_map`: throws `type_error.302` if the value is not an object; otherwise,
|
||||
whatever converting a member to the mapped type throws.
|
||||
- For `#!cpp std::map`/`#!cpp std::unordered_map` of views: throws `type_error.302` if the value is not an object.
|
||||
- For a `T` whose `from_json()` reads the view: whatever that `from_json()` throws; for the library's conversions and
|
||||
the macros, the same exceptions with the same messages as [`BasicJsonType::get<T>()`](../basic_json/get.md) of the
|
||||
same value.
|
||||
- For every other `T`: whatever [`materialize().get<T>()`](../basic_json/get.md) throws -- typically `type_error.302`,
|
||||
or whatever a user-provided `from_json()` throws.
|
||||
|
||||
None of the exceptions thrown directly by this function (the first three bullets above) carry a
|
||||
None of the exceptions thrown directly by this function or by a `from_json()` that reads the view (the first four
|
||||
bullets above) carry a
|
||||
[`JSON_DIAGNOSTICS`](../macros/json_diagnostics.md) path: the view has no `BasicJsonType` value to point at. An
|
||||
exception thrown while converting through `materialize()` (the last bullet) is different: it is thrown by a real
|
||||
`BasicJsonType` value, so it **does** carry a `JSON_DIAGNOSTICS` path if `BasicJsonType` was built with it enabled.
|
||||
@@ -76,6 +99,8 @@ document.
|
||||
- `#!cpp std::map`/`#!cpp std::unordered_map`: linear in the number of members for walking them, plus the container's
|
||||
own insertion cost per member (logarithmic for `#!cpp std::map`, amortized constant for `#!cpp
|
||||
std::unordered_map`), times the complexity of converting one member to the mapped type.
|
||||
- a `T` whose `from_json()` reads the view: the cost of that `from_json()`; for the macros, linear in the number of
|
||||
members times the cost of a lookup, plus the cost of converting the members.
|
||||
- every other `T`: the cost of [`materialize()`](materialize.md) and of destroying the `BasicJsonType` value
|
||||
afterwards, plus that of [`BasicJsonType::get<T>()`](../basic_json/get.md).
|
||||
|
||||
@@ -116,8 +141,8 @@ document.
|
||||
#include <string>
|
||||
#include <vector>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using json_view = nlohmann::json_view;
|
||||
using nlohmann::json_document;
|
||||
using nlohmann::json_view;
|
||||
|
||||
// address has no direct conversion in get<T>(), so get<address>() falls back
|
||||
// to materialize().get<address>() -- a real nlohmann::json value is built
|
||||
|
||||
@@ -1,12 +1,12 @@
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/get/" rel="canonical"><link href=../front/ rel=prev><link href=../get_string/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>get - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> get </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" 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12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5"/></svg> </label> Line truncated
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/get/" rel="canonical"><link href=../front/ rel=prev><link href=../get_string/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>get - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> get </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5"/></svg> </label> Line truncated
|
||||
<span class=n>T</span><span class=w> </span><span class=n>get</span><span class=p>()</span><span class=w> </span><span class=k>const</span><span class=p>;</span>
|
||||
</code></pre></div> <p>Converts the value to <code>T</code>.</p> <p>For the types below, the conversion works directly on the flat index -- no <code>BasicJsonType</code> value is built for it:</p> <ul> <li><code class=highlight><span class=kt>bool</span></code></li> <li>arithmetic types other than <code class=highlight><span class=kt>bool</span></code> (for a boolean, <code class=highlight><span class=mi>0</span></code>/<code class=highlight><span class=mi>1</span></code>, exactly as for <a href=../../basic_json/get/ ><code>BasicJsonType::get<T>()</code></a>)</li> <li><code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>nullptr_t</span></code></li> <li><code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>basic_string</span><span class=o><</span><span class=kt>char</span><span class=p>,</span><span class=w> </span><span class=n>Traits</span><span class=p>,</span><span class=w> </span><span class=n>Alloc</span><span class=o>></span></code> (including <code>string_t</code>) -- a copy of the string</li> <li><a href=../#member-types><code>string_view_t</code></a> -- <strong>no copy</strong>: the returned view points into the document's <a href=../../basic_json_document/source/ ><code>source()</code></a> text, or, for a string that contains escape sequences, into the document's own buffer of decoded strings (see <a href=../get_string/ ><code>get_string()</code></a>)</li> <li><code>BasicJsonType</code> -- equivalent to <a href=../materialize/ ><code>materialize()</code></a></li> <li><code>basic_json_view</code> -- returns <code class=highlight><span class=o>*</span><span class=k>this</span></code></li> <li><code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>vector</span><span class=o><</span><span class=n>U</span><span class=p>,</span><span class=w> </span><span class=n>A</span><span class=o>></span></code> -- from an array, element by element, each converted with <code class=highlight><span class=n>get</span><span class=o><</span><span class=n>U</span><span class=o>></span><span class=p>()</span></code>; <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>vector</span><span class=o><</span><span class=n>basic_json_view</span><span class=o>></span></code> keeps a view of every element instead of a value</li> <li><code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>map</span><span class=o><</span><span class=n>K</span><span class=p>,</span><span class=w> </span><span class=n>V</span><span class=p>,</span><span class=w> </span><span class=n>C</span><span class=p>,</span><span class=w> </span><span class=n>A</span><span class=o>></span></code> and <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>unordered_map</span><span class=o><</span><span class=n>K</span><span class=p>,</span><span class=w> </span><span class=n>V</span><span class=p>,</span><span class=w> </span><span class=n>H</span><span class=p>,</span><span class=w> </span><span class=n>E</span><span class=p>,</span><span class=w> </span><span class=n>A</span><span class=o>></span></code>, if <code>K</code> is constructible from a <code class=highlight><span class=p>(</span><span class=k>const</span><span class=w> </span><span class=kt>char</span><span class=o>*</span><span class=p>,</span><span class=w> </span><span class=n>std</span><span class=o>::</span><span class=kt>size_t</span><span class=p>)</span></code> pair -- from an object, member by member, each value converted with <code class=highlight><span class=n>get</span><span class=o><</span><span class=n>V</span><span class=o>></span><span class=p>()</span></code>; with a repeated key, the <em>last</em> value is kept, as <a href=../../basic_json/parse/ ><code>BasicJsonType::parse()</code></a> (and <a href=../materialize/ ><code>materialize()</code></a>) does; <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>map</span><span class=o><</span><span class=n>std</span><span class=o>::</span><span class=n>string</span><span class=p>,</span><span class=w> </span><span class=n>basic_json_view</span><span class=o>></span></code> keeps views of the members instead of values</li> </ul> <p>Every other <code>T</code> -- <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>list</span></code>, <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>pair</span></code>, <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>array</span></code>, enumerations, user types with a <code>from_json()</code>, ... -- is converted by <code class=highlight><span class=n>materialize</span><span class=p>().</span><span class=n>get</span><span class=o><</span><span class=n>T</span><span class=o>></span><span class=p>()</span></code>: the subtree is built into a real <code>BaLine truncated
|
||||
</code></pre></div> <p>Converts the value to <code>T</code>.</p> <p>For the types below, the conversion works directly on the flat index -- no <code>BasicJsonType</code> value is built for it:</p> <ul> <li><code class=highlight><span class=kt>bool</span></code></li> <li>arithmetic types other than <code class=highlight><span class=kt>bool</span></code> (for a boolean, <code class=highlight><span class=mi>0</span></code>/<code class=highlight><span class=mi>1</span></code>, exactly as for <a href=../../basic_json/get/ ><code>BasicJsonType::get<T>()</code></a>)</li> <li><code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>nullptr_t</span></code></li> <li><code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>basic_string</span><span class=o><</span><span class=kt>char</span><span class=p>,</span><span class=w> </span><span class=n>Traits</span><span class=p>,</span><span class=w> </span><span class=n>Alloc</span><span class=o>></span></code> (including <code>string_t</code>) -- a copy of the string</li> <li><a href=../#member-types><code>string_view_t</code></a> -- <strong>no copy</strong>: the returned view points into the document's <a href=../../basic_json_document/source/ ><code>source()</code></a> text, or, for a string that contains escape sequences, into the document's own buffer of decoded strings (see <a href=../get_string/ ><code>get_string()</code></a>)</li> <li><code>BasicJsonType</code> -- equivalent to <a href=../materialize/ ><code>materialize()</code></a></li> <li><code>basic_json_view</code> -- returns <code class=highlight><span class=o>*</span><span class=k>this</span></code></li> <li><code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>vector</span><span class=o><</span><span class=n>U</span><span class=p>,</span><span class=w> </span><span class=n>A</span><span class=o>></span></code> of the types above -- from an array, element by element, each converted with <code class=highlight><span class=n>get</span><span class=o><</span><span class=n>U</span><span class=o>></span><span class=p>()</span></code>; <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>vector</span><span class=o><</span><span class=n>basic_json_view</span><span class=o>></span></code> keeps a view of every element instead of a value</li> <li><code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>map</span><span class=o><</span><span class=n>K</span><span class=p>,</span><span class=w> </span><span class=n>basic_json_view</span><span class=p>,</span><span class=w> </span><span class=n>C</span><span class=p>,</span><span class=w> </span><span class=n>A</span><span class=o>></span></code> and <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>unordered_map</span><span class=o><</span><span class=n>K</span><span class=p>,</span><span class=w> </span><span class=n>basic_json_view</span><span class=p>,</span><span class=w> </span><span class=n>H</span><span class=p>,</span><span class=w> </span><span class=n>E</span><span class=p>,</span><span class=w> </span><span class=n>A</span><span class=o>></span></code>, if <code>K</code> is constructible from a <code class=highlight><span class=p>(</span><span class=k>const</span><span class=w> </span><span class=kt>char</span><span class=o>*</span><span class=p>,</span><span class=w> </span><span class=n>std</span><span class=o>::</span><span class=kt>size_t</span><span class=p>)</span></code> pair -- views of the members of an object; with a repeated key, the view of the <em>last</em> member is kept, as <a href=../../basic_json/parse/ ><code>BasicJsonType::parse()</code></a> keeps its value</li> </ul> <p>A default-constructible <code>T</code> whose <code>from_json()</code> accepts views reads the view directly as well, without building a <code>BasicJsonType</code> value. This covers the library's own conversions of the standard library types -- all other <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>vector</span></code>s, <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>map</span></code>/<code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>unordered_map</span></code> (also with other key types), <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>list</span></code>, <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>deque</span></code>, <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>set</span></code>, <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>forward_list</span></code>, <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>valarray</span></code>, <code class=highlight><span class=n>std</span><span clasLine truncated
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json_view.hpp></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><string></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><vector></span>
|
||||
|
||||
<span class=k>using</span><span class=w> </span><span class=n>json_document</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>json_view</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_view</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_view</span><span class=p>;</span>
|
||||
|
||||
<span class=c1>// address has no direct conversion in get<T>(), so get<address>() falls back</span>
|
||||
<span class=c1>// to materialize().get<address>() -- a real nlohmann::json value is built</span>
|
||||
@@ -58,4 +58,4 @@
|
||||
</code></pre></div> <p>Output:</p> <div class=highlight><pre><span></span><code><span class=err>Alice</span><span class=w> </span><span class=err>(ac</span><span class=kc>t</span><span class=err>ive)</span>
|
||||
<span class=mi>1</span><span class=w> </span><span class=mi>2</span><span class=w> </span><span class=mi>3</span>
|
||||
<span class=err>Berli</span><span class=kc>n</span><span class=w> </span><span class=mi>10115</span>
|
||||
</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">¶</a></h2> <ul> <li><a href=../get_to/ >get_to</a> - convert and write into a passed value</li> <li><a href=../get_string/ >get_string</a> - the string, without a copy</li> <li><a href=../number_token/ >number_token</a> - a number's token text, without a copy</li> <li><a href=../materialize/ >materialize</a> - build the <code>BasicJsonType</code> value of this subtree</li> <li><a href=../../basic_json/get/ ><code>BasicJsonType::get</code></a> - the corresponding function of <code>basic_json</code></li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">¶</a></h2> <ul> <li>Added in version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="October 21, 2026 08:21:27 UTC">October 21, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright © 2013-2026 Niels Lohmann </div> </div> <div class=md-social> <a href="https://github.com/nlohmann" target="_blank" rel="noopener" title="github.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 512 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><path d="M173.9 397.4c0 2-2.3 3.6-5.2 3.6-3.3.3-5.6-1.3-5.6-3.6 0-2 2.3-3.6 5.2-3.6 3-.3 5.6 1.3 5.6 3.6m-31.1-4.5c-.7 2 1.3 4.3 4.3 4.9 2.6 1 5.6 0 6.2-2s-1.3-4.3-4.3-5.2c-2.6-.7-5.5.3-6.2 2.3m44.2-1.7c-2.9.7-4.9 2.6-4.6 4.9.3 2 2.9 3.3 5.9 2.6 2.9-.7 4.9-2.6 4.6-4.6-.3-1.9-3-3.2-5.9-2.9M252.8 8C114.1 8 8 113.3 8 252c0 110.9 69.8 205.8 169.5 239.2 12.8 2.3 17.3-5.6 17.3-12.1 0-6.2-.3-40.4-.3-61.4 0 0-70 15-84.7-29.8 0 0-11.4-29.1-27.8-36.6 0 0-22.9-15.7 1.6-15.4 0 0 24.9 2 38.6 25.8 21.9 38.6 58.6 27.5 72.9 20.9 2.3-16 8.8-27.1 16-33.7-55.9-6.2-112.3-14.3-112.3-110.5 0-27.5 7.6-41.3 23.6-58.9-2.6-6.5-11.1-33.3 2.6-67.9 20.9-6.5 69 27 69 27 20-5.6 41.5-8.5 62.8-8.5s42.8 2.9 62.8 8.5c0 0 48.1-33.6 69-27 13.7 34.7 5.2 61.4 2.6 67.9 16 17.7 25.8 31.5 25.8 58.9 0 96.5-58.9 104.2-114.8 110.5 9.2 7.9 17 22.9 17 46.4 0 33.7-.3 75.4-.3 83.6 0 6.5 4.6 14.4 17.3 12.1C436.2 457.8 504 362.9 504 252 504 113.3 391.5 8 252.8 8M105.2 352.9c-1.3 1-1 3.3.7 5.2 1.6 1.6 3.9 2.3 5.2 1 1.3-1 1-3.3-.7-5.2-1.6-1.6-3.9-2.3-5.2-1m-10.8-8.1c-.7 1.3.3 2.9 2.3 3.9 1.6 1 3.6.7 4.3-.7.7-1.3-.3-2.9-2.3-3.9-2-.6-3.6-.3-4.3.7m32.4 35.6c-1.6 1.3-1 4.3 1.3 6.2 2.3 2.3 5.2 2.6 6.5 1 1.3-1.3.7-4.3-1.3-6.2-2.2-2.3-5.2-2.6-6.5-1m-11.4-14.7c-1.6 1-1.6 3.6 0 5.9s4.3 3.3 5.6 2.3c1.6-1.3 1.6-3.9 0-6.2-1.4-2.3-4-3.3-5.6-2"/></svg> </a> <a href="https://www.linkedin.com/in/nielslohmann/" target="_blank" rel="noopener" title="www.linkedin.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 448 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><path d="M416 32H31.9C14.3 32 0 46.5 0 64.3v383.4C0 465.5 14.3 480 31.9 480H416c17.6 0 32-14.5 32-32.3V64.3c0-17.8-14.4-32.3-32-32.3M135.4 416H69V202.2h66.5V416zM102.2 96a38.5 38.5 0 1 1 0 77 38.5 38.5 0 1 1 0-7Line truncated
|
||||
</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">¶</a></h2> <ul> <li><a href=../get_to/ >get_to</a> - convert and write into a passed value</li> <li><a href=../get_string/ >get_string</a> - the string, without a copy</li> <li><a href=../number_token/ >number_token</a> - a number's token text, without a copy</li> <li><a href=../materialize/ >materialize</a> - build the <code>BasicJsonType</code> value of this subtree</li> <li><a href=../../basic_json/get/ ><code>BasicJsonType::get</code></a> - the corresponding function of <code>basic_json</code></li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">¶</a></h2> <ul> <li>Added in version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="October 26, 2026 19:13:32 UTC">October 26, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright © 2013-2026 Niels Lohmann </div> </div> <div class=md-social> <a href="https://github.com/nlohmann" target="_blank" rel="noopener" title="github.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 512 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><path d="M173.9 397.4c0 2-2.3 3.6-5.2 3.6-3.3.3-5.6-1.3-5.6-3.6 0-2 2.3-3.6 5.2-3.6 3-.3 5.6 1.3 5.6 3.6m-31.1-4.5c-.7 2 1.3 4.3 4.3 4.9 2.6 1 5.6 0 6.2-2s-1.3-4.3-4.3-5.2c-2.6-.7-5.5.3-6.2 2.3m44.2-1.7c-2.9.7-4.9 2.6-4.6 4.9.3 2 2.9 3.3 5.9 2.6 2.9-.7 4.9-2.6 4.6-4.6-.3-1.9-3-3.2-5.9-2.9M252.8 8C114.1 8 8 113.3 8 252c0 110.9 69.8 205.8 169.5 239.2 12.8 2.3 17.3-5.6 17.3-12.1 0-6.2-.3-40.4-.3-61.4 0 0-70 15-84.7-29.8 0 0-11.4-29.1-27.8-36.6 0 0-22.9-15.7 1.6-15.4 0 0 24.9 2 38.6 25.8 21.9 38.6 58.6 27.5 72.9 20.9 2.3-16 8.8-27.1 16-33.7-55.9-6.2-112.3-14.3-112.3-110.5 0-27.5 7.6-41.3 23.6-58.9-2.6-6.5-11.1-33.3 2.6-67.9 20.9-6.5 69 27 69 27 20-5.6 41.5-8.5 62.8-8.5s42.8 2.9 62.8 8.5c0 0 48.1-33.6 69-27 13.7 34.7 5.2 61.4 2.6 67.9 16 17.7 25.8 31.5 25.8 58.9 0 96.5-58.9 104.2-114.8 110.5 9.2 7.9 17 22.9 17 46.4 0 33.7-.3 75.4-.3 83.6 0 6.5 4.6 14.4 17.3 12.1C436.2 457.8 504 362.9 504 252 504 113.3 391.5 8 252.8 8M105.2 352.9c-1.3 1-1 3.3.7 5.2 1.6 1.6 3.9 2.3 5.2 1 1.3-1 1-3.3-.7-5.2-1.6-1.6-3.9-2.3-5.2-1m-10.8-8.1c-.7 1.3.3 2.9 2.3 3.9 1.6 1 3.6.7 4.3-.7.7-1.3-.3-2.9-2.3-3.9-2-.6-3.6-.3-4.3.7m32.4 35.6c-1.6 1.3-1 4.3 1.3 6.2 2.3 2.3 5.2 2.6 6.5 1 1.3-1.3.7-4.3-1.3-6.2-2.2-2.3-5.2-2.6-6.5-1m-11.4-14.7c-1.6 1-1.6 3.6 0 5.9s4.3 3.3 5.6 2.3c1.6-1.3 1.6-3.9 0-6.2-1.4-2.3-4-3.3-5.6-2"/></svg> </a> <a href="https://www.linkedin.com/in/nielslohmann/" target="_blank" rel="noopener" title="www.linkedin.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 448 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><path d="M416 32H31.9C14.3 32 0 46.5 0 64.3v383.4C0 465.5 14.3 480 31.9 480H416c17.6 0 32-14.5 32-32.3V64.3c0-17.8-14.4-32.3-32-32.3M135.4 416H69V202.2h66.5V416zM102.2 96a38.5 38.5 0 1 1 0 77 38.5 38.5 0 1 1 0-7Line truncated
|
||||
@@ -16,10 +16,16 @@ For the types below, the conversion works directly on the flat index -- no `Basi
|
||||
- [`string_view_t`](https://json.nlohmann.me/api/basic_json_view/#member-types) -- **no copy**: the returned view points into the document's [`source()`](https://json.nlohmann.me/api/basic_json_document/source/index.md) text, or, for a string that contains escape sequences, into the document's own buffer of decoded strings (see [`get_string()`](https://json.nlohmann.me/api/basic_json_view/get_string/index.md))
|
||||
- `BasicJsonType` -- equivalent to [`materialize()`](https://json.nlohmann.me/api/basic_json_view/materialize/index.md)
|
||||
- `basic_json_view` -- returns `*this`
|
||||
- `std::vector<U, A>` -- from an array, element by element, each converted with `get<U>()`; `std::vector<basic_json_view>` keeps a view of every element instead of a value
|
||||
- `std::map<K, V, C, A>` and `std::unordered_map<K, V, H, E, A>`, if `K` is constructible from a `(const char*, std::size_t)` pair -- from an object, member by member, each value converted with `get<V>()`; with a repeated key, the *last* value is kept, as [`BasicJsonType::parse()`](https://json.nlohmann.me/api/basic_json/parse/index.md) (and [`materialize()`](https://json.nlohmann.me/api/basic_json_view/materialize/index.md)) does; `std::map<std::string, basic_json_view>` keeps views of the members instead of values
|
||||
- `std::vector<U, A>` of the types above -- from an array, element by element, each converted with `get<U>()`; `std::vector<basic_json_view>` keeps a view of every element instead of a value
|
||||
- `std::map<K, basic_json_view, C, A>` and `std::unordered_map<K, basic_json_view, H, E, A>`, if `K` is constructible from a `(const char*, std::size_t)` pair -- views of the members of an object; with a repeated key, the view of the *last* member is kept, as [`BasicJsonType::parse()`](https://json.nlohmann.me/api/basic_json/parse/index.md) keeps its value
|
||||
|
||||
Every other `T` -- `std::list`, `std::pair`, `std::array`, enumerations, user types with a `from_json()`, ... -- is converted by `materialize().get<T>()`: the subtree is built into a real `BasicJsonType` value first (as [`BasicJsonType::parse()`](https://json.nlohmann.me/api/basic_json/parse/index.md) would), and converted from there exactly as [`BasicJsonType::get<T>()`](https://json.nlohmann.me/api/basic_json/get/index.md) would convert it.
|
||||
A default-constructible `T` whose `from_json()` accepts views reads the view directly as well, without building a `BasicJsonType` value. This covers the library's own conversions of the standard library types -- all other `std::vector`s, `std::map`/`std::unordered_map` (also with other key types), `std::list`, `std::deque`, `std::set`, `std::forward_list`, `std::valarray`, `std::array`, C arrays, `std::pair`, `std::tuple`, `std::optional`, enumerations, `std::filesystem::path`, ... -- which give the same values as `materialize().get<T>()` (from an object, a repeated key keeps the *last* value, as [`BasicJsonType::parse()`](https://json.nlohmann.me/api/basic_json/parse/index.md) does), as well as the types of the [`NLOHMANN_DEFINE_TYPE_*`](https://json.nlohmann.me/api/macros/nlohmann_define_type_intrusive/index.md) and [`NLOHMANN_DEFINE_DERIVED_TYPE_*`](https://json.nlohmann.me/api/macros/nlohmann_define_derived_type/index.md) macros and the enumerations of [`NLOHMANN_JSON_SERIALIZE_ENUM`](https://json.nlohmann.me/api/macros/nlohmann_json_serialize_enum/index.md), and any `from_json()` constrained to accept views, e.g. with [`is_json_view`](https://json.nlohmann.me/api/is_json_view/index.md). A `from_json()` that also accepts types that are no JSON values at all, such as the unconstrained `template<typename BasicJsonType> void from_json(const BasicJsonType&,T&)` of [arbitrary type conversions](https://json.nlohmann.me/features/arbitrary_types/index.md), is not called with a view: it may use `BasicJsonType` functions a view does not have. See [Writing generic code](https://json.nlohmann.me/features/json_view/#writing-generic-code).
|
||||
|
||||
Duplicate keys
|
||||
|
||||
Such a `from_json()` looks members up in the view, where a repeated key finds the **first** member, while `materialize().get<T>()` sees the **last** one, as [`BasicJsonType::parse()`](https://json.nlohmann.me/api/basic_json/parse/index.md) keeps it: for `{"x":1,"x":2}`, `get<point>()` reads `x == 1`. See [Duplicate keys](https://json.nlohmann.me/features/json_view/#duplicate-keys).
|
||||
|
||||
Every other `T` -- user types whose `from_json()` is written for `BasicJsonType` only, types without a default constructor, `std::tuple`s holding references, ... -- is converted by `materialize().get<T>()`: the subtree is built into a real `BasicJsonType` value first (as [`BasicJsonType::parse()`](https://json.nlohmann.me/api/basic_json/parse/index.md) would), and converted from there exactly as [`BasicJsonType::get<T>()`](https://json.nlohmann.me/api/basic_json/get/index.md) would convert it.
|
||||
|
||||
## Template parameters
|
||||
|
||||
@@ -37,10 +43,11 @@ Strong guarantee: there are no changes to the view or the document it refers to.
|
||||
|
||||
- For the directly-converted types listed above (other than `BasicJsonType` and `basic_json_view`, which never throw): throws [`type_error.302`](https://json.nlohmann.me/home/exceptions/#jsonexceptiontype_error302) if the value's type does not match `T` -- the same exception, with the same message, that [`BasicJsonType::get<T>()`](https://json.nlohmann.me/api/basic_json/get/index.md) throws for the same JSON type and `T`.
|
||||
- For `std::vector<U, A>`: throws `type_error.302` if the value is not an array; otherwise, whatever converting an element to `U` throws.
|
||||
- For `std::map`/`std::unordered_map`: throws `type_error.302` if the value is not an object; otherwise, whatever converting a member to the mapped type throws.
|
||||
- For `std::map`/`std::unordered_map` of views: throws `type_error.302` if the value is not an object.
|
||||
- For a `T` whose `from_json()` reads the view: whatever that `from_json()` throws; for the library's conversions and the macros, the same exceptions with the same messages as [`BasicJsonType::get<T>()`](https://json.nlohmann.me/api/basic_json/get/index.md) of the same value.
|
||||
- For every other `T`: whatever [`materialize().get<T>()`](https://json.nlohmann.me/api/basic_json/get/index.md) throws -- typically `type_error.302`, or whatever a user-provided `from_json()` throws.
|
||||
|
||||
None of the exceptions thrown directly by this function (the first three bullets above) carry a [`JSON_DIAGNOSTICS`](https://json.nlohmann.me/api/macros/json_diagnostics/index.md) path: the view has no `BasicJsonType` value to point at. An exception thrown while converting through `materialize()` (the last bullet) is different: it is thrown by a real `BasicJsonType` value, so it **does** carry a `JSON_DIAGNOSTICS` path if `BasicJsonType` was built with it enabled. That path is relative to the root of the view's subtree, because `materialize()` builds only the subtree (with parent pointers): it is empty if the failing value is the subtree's root itself, and it never is the path within the whole document.
|
||||
None of the exceptions thrown directly by this function or by a `from_json()` that reads the view (the first four bullets above) carry a [`JSON_DIAGNOSTICS`](https://json.nlohmann.me/api/macros/json_diagnostics/index.md) path: the view has no `BasicJsonType` value to point at. An exception thrown while converting through `materialize()` (the last bullet) is different: it is thrown by a real `BasicJsonType` value, so it **does** carry a `JSON_DIAGNOSTICS` path if `BasicJsonType` was built with it enabled. That path is relative to the root of the view's subtree, because `materialize()` builds only the subtree (with parent pointers): it is empty if the failing value is the subtree's root itself, and it never is the path within the whole document.
|
||||
|
||||
## Complexity
|
||||
|
||||
@@ -49,6 +56,7 @@ None of the exceptions thrown directly by this function (the first three bullets
|
||||
- `BasicJsonType`: linear in the size of the subtree, see [`materialize()`](https://json.nlohmann.me/api/basic_json_view/materialize/index.md).
|
||||
- `std::vector<U, A>`: linear in the number of elements, times the complexity of converting one element to `U`.
|
||||
- `std::map`/`std::unordered_map`: linear in the number of members for walking them, plus the container's own insertion cost per member (logarithmic for `std::map`, amortized constant for `std::unordered_map`), times the complexity of converting one member to the mapped type.
|
||||
- a `T` whose `from_json()` reads the view: the cost of that `from_json()`; for the macros, linear in the number of members times the cost of a lookup, plus the cost of converting the members.
|
||||
- every other `T`: the cost of [`materialize()`](https://json.nlohmann.me/api/basic_json_view/materialize/index.md) and of destroying the `BasicJsonType` value afterwards, plus that of [`BasicJsonType::get<T>()`](https://json.nlohmann.me/api/basic_json/get/index.md).
|
||||
|
||||
## Notes
|
||||
@@ -77,8 +85,8 @@ The example below reads typed fields straight into C++ variables, collects a vie
|
||||
#include <string>
|
||||
#include <vector>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using json_view = nlohmann::json_view;
|
||||
using nlohmann::json_document;
|
||||
using nlohmann::json_view;
|
||||
|
||||
// address has no direct conversion in get<T>(), so get<address>() falls back
|
||||
// to materialize().get<address>() -- a real nlohmann::json value is built
|
||||
|
||||
@@ -60,8 +60,8 @@ since floating-point values and unescaped strings are read from the source lazil
|
||||
#include <nlohmann/json_view.hpp>
|
||||
#include <string>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using json_view = nlohmann::json_view;
|
||||
using nlohmann::json_document;
|
||||
using nlohmann::json_view;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -1,10 +1,10 @@
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/get_string/" rel="canonical"><link href=../get/ rel=prev><link href=../get_to/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>get_string - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/get_string/" rel="canonical"><link href=../get/ rel=prev><link href=../get_to/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>get_string - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#nlohmannbasic_json_viewget_string class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> get_string </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark 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4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.Line truncated
|
||||
</code></pre></div> <p>Returns the string value as a <a href=../#member-types><code>string_view_t</code></a>, without copying it.</p> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">¶</a></h2> <p>The string, as a <a href=../#member-types><code>string_view_t</code></a> that points either into the document's <a href=../../basic_json_document/source/ ><code>source()</code></a> text (a string with no escape sequences), or into the document's own buffer of decoded strings (a string that contains escape sequences, such as <code class=highlight><span class=s2>"\n"</span></code> or <code class=highlight><span class=s2>"\u00e9"</span></code>, which had to be decoded once when the document was parsed).</p> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">¶</a></h2> <p>Strong guarantee: there are no changes to the view or the document it refers to.</p> <h2 id=exceptions>Exceptions<a class=headerlink href=#exceptions title="Permanent link">¶</a></h2> <p>Throws <a href=../../../home/exceptions/#jsonexceptiontype_error302><code>type_error.302</code></a> if the value is not a string; example: <code>"type must be string, but is array"</code>.</p> <p>This exception does not carry a <a href=../../macros/json_diagnostics/ ><code>JSON_DIAGNOSTICS</code></a> path: the view has no <code>BasicJsonType</code> value to point at, so the exception is created without one, even if <code>BasicJsonType</code> was built with <code>JSON_DIAGNOSTICS</code> enabled.</p> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">¶</a></h2> <p>Constant.</p> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">¶</a></h2> <p><code>basic_json_view</code> has no <code>BasicJsonType</code> value stored anywhere, so unlike <code>BasicJsonType</code>, it has no <code>get_ref()</code> to hand out a reference to a stored <code>string_t</code>. <code>get_string()</code> (equivalently, <a href=../get/ ><code>get<string_view_t>()</code></a>) is the zero-copy alternative: <a href=../../basic_json/get_ref/ ><code>BasicJsonType::get_ref<const string_t&>()</code></a> is its closest counterpart, except that it returns a view instead of a reference to a value that must already exist.</p> <p><code>get_string()</code> borrows the string: nothing is copied, whereas <a href=../get/ ><code>get<std::string>()</code></a> copies it. For a borrowed document, the returned <a href=../#member-types><code>string_view_t</code></a> is valid as long as the caller's buffer; for an owned one, as long as the document.</p> <p>The returned <a href=../#member-types><code>string_view_t</code></a> is valid exactly as long as the view that produced it -- see the <a href=../ >validity rules</a> of <code>basic_json_view</code> -- and, for a string with no escapes, for as long as the document's source text, which for a borrowed document must remain valid <strong>and unmodified</strong> for as long as the document exists, since floating-point values and unescaped strings are read from the source lazily.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">¶</a></h2> <details class=example> <summary>Example</summary> <p>The example below pulls one field out of a <abbr title="JavaScript Object Notation">JSON</abbr> text that stands in for a large <abbr title="Application Programming Interface">API</abbr> response, and shows that no <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>string</span></code> was allocated for it: the returned view still points inside the original buffer. A field that contains an escape sequence cannot point into the original text -- it was decoded once into the document's own buffer instead -- but still avoids a per-field allocation.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><iostream></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json_view.hpp></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><string></span>
|
||||
|
||||
<span class=k>using</span><span class=w> </span><span class=n>json_document</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>json_view</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_view</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_view</span><span class=p>;</span>
|
||||
|
||||
<span class=kt>int</span><span class=w> </span><span class=nf>main</span><span class=p>()</span>
|
||||
<span class=p>{</span>
|
||||
|
||||
@@ -43,8 +43,8 @@ The example below pulls one field out of a JSON text that stands in for a large
|
||||
#include <nlohmann/json_view.hpp>
|
||||
#include <string>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using json_view = nlohmann::json_view;
|
||||
using nlohmann::json_document;
|
||||
using nlohmann::json_view;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -5,12 +5,13 @@ template<typename T>
|
||||
T& get_to(T& v) const;
|
||||
```
|
||||
|
||||
Converts the value to `T` and stores it in `v`, in one of two ways:
|
||||
Converts the value to `T` and stores it in `v`, in one of three ways:
|
||||
|
||||
- For the types that [`get<T>()`](get.md) converts directly -- arithmetic types, `#!cpp bool`,
|
||||
`#!cpp std::nullptr_t`, [`string_view_t`](index.md#member-types), `#!cpp std::basic_string`, `BasicJsonType`,
|
||||
`basic_json_view`, `#!cpp std::vector`, and `#!cpp std::map`/`#!cpp std::unordered_map` with string keys -- `v` is
|
||||
assigned: `#!cpp v = get<T>()`.
|
||||
`basic_json_view`, vectors of these, and maps of views -- `v` is assigned: `#!cpp v = get<T>()`.
|
||||
- For a type whose `from_json()` accepts views (see [`get<T>()`](get.md)), that `from_json()` is called with the
|
||||
view and the existing `v`, without building a `BasicJsonType` value.
|
||||
- For every other type, the subtree is built into a `BasicJsonType` value and `#!cpp materialize().get_to(v)` is
|
||||
called, i.e. `from_json()` is invoked with the existing `v`, exactly as
|
||||
[`BasicJsonType::get_to()`](../basic_json/get_to.md) does.
|
||||
@@ -65,8 +66,8 @@ them with those of a default-constructed `T`.
|
||||
#include <nlohmann/json_view.hpp>
|
||||
#include <string>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using json_view = nlohmann::json_view;
|
||||
using nlohmann::json_document;
|
||||
using nlohmann::json_view;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -1,11 +1,11 @@
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/get_to/" rel="canonical"><link href=../get_string/ rel=prev><link href=../is_array/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>get_to - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#nlohmannbasic_json_viewget_to class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> get_to </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark 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4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5"/><Line truncated
|
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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/get_to/" rel="canonical"><link href=../get_string/ rel=prev><link href=../is_array/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>get_to - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#nlohmannbasic_json_viewget_to class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> get_to </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark 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4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5"/><Line truncated
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<span class=n>T</span><span class=o>&</span><span class=w> </span><span class=n>get_to</span><span class=p>(</span><span class=n>T</span><span class=o>&</span><span class=w> </span><span class=n>v</span><span class=p>)</span><span class=w> </span><span class=k>const</span><span class=p>;</span>
|
||||
</code></pre></div> <p>Converts the value to <code>T</code> and stores it in <code>v</code>, in one of two ways:</p> <ul> <li>For the types that <a href=../get/ ><code>get<T>()</code></a> converts directly -- arithmetic types, <code class=highlight><span class=kt>bool</span></code>, <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>nullptr_t</span></code>, <a href=../#member-types><code>string_view_t</code></a>, <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>basic_string</span></code>, <code>BasicJsonType</code>, <code>basic_json_view</code>, <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>vector</span></code>, and <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>map</span></code>/<code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>unordered_map</span></code> with string keys -- <code>v</code> is assigned: <code class=highlight><span class=n>v</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>get</span><span class=o><</span><span class=n>T</span><span class=o>></span><span class=p>()</span></code>.</li> <li>For every other type, the subtree is built into a <code>BasicJsonType</code> value and <code class=highlight><span class=n>materialize</span><span class=p>().</span><span class=n>get_to</span><span class=p>(</span><span class=n>v</span><span class=p>)</span></code> is called, i.e. <code>from_json()</code> is invoked with the existing <code>v</code>, exactly as <a href=../../basic_json/get_to/ ><code>BasicJsonType::get_to()</code></a> does.</li> </ul> <h2 id=template-parameters>Template parameters<a class=headerlink href=#template-parameters title="Permanent link">¶</a></h2> <dl> <dt><code>T</code></dt> <dd>the type to convert the value to</dd> </dl> <h2 id=parameters>Parameters<a class=headerlink href=#parameters title="Permanent link">¶</a></h2> <dl> <dt><code>v</code> (out)</dt> <dd>the variable to store the converted value in</dd> </dl> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">¶</a></h2> <p><code>v</code>, allowing calls to chain</p> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">¶</a></h2> <ul> <li>For the directly converted types: strong exception safety. If an exception is thrown, <code>v</code> is not modified.</li> <li>For every other type: as for <a href=../../basic_json/get_to/ ><code>BasicJsonType::get_to()</code></a>. <code>materialize()</code> throws before <code>v</code> is touched, but a <code>from_json()</code> that throws may leave <code>v</code> partly modified.</li> </ul> <h2 id=exceptions>Exceptions<a class=headerlink href=#exceptions title="Permanent link">¶</a></h2> <ul> <li>For the directly converted types: whatever <a href=../get/ ><code>get<T>()</code></a> throws for the same value and <code>T</code>.</li> <li>For every other type: whatever <a href=../materialize/ ><code>materialize()</code></a> and <a href=../../basic_json/get_to/ ><code>BasicJsonType::get_to()</code></a> throw.</li> </ul> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">¶</a></h2> <ul> <li>For the directly converted types: whatever <a href=../get/ ><code>get<T>()</code></a> has for the same <code>T</code>.</li> <li>For every other type: that of <a href=../materialize/ ><code>materialize()</code></a>, plus that of <a href=../../basic_json/get_to/ ><code>BasicJsonType::get_to()</code></a>.</li> </ul> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">¶</a></h2> <p>The difference between the two ways matters for a <code>from_json()</code> that sets only the fields present in the <abbr title="JavaScript Object Notation">JSON</abbr>: since it runs on the existing <code>v</code>, the other fields of <code>v</code> keep their values, whereas assigning <code>get<T>()</code> would replace them with those of a default-constructed <code>T</code>.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">¶</a></h2> <details class=example> <summary>Example</summary> <p>The example below reads several fields of a service configuration directly into existing variables, then uses the returned reference to fold the <code class=highlight><span class=n>host</span></code>/<code class=highlight><span class=n>port</span></code> pair into a single string in the same expression.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><iostream></span>
|
||||
</code></pre></div> <p>Converts the value to <code>T</code> and stores it in <code>v</code>, in one of three ways:</p> <ul> <li>For the types that <a href=../get/ ><code>get<T>()</code></a> converts directly -- arithmetic types, <code class=highlight><span class=kt>bool</span></code>, <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>nullptr_t</span></code>, <a href=../#member-types><code>string_view_t</code></a>, <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>basic_string</span></code>, <code>BasicJsonType</code>, <code>basic_json_view</code>, vectors of these, and maps of views -- <code>v</code> is assigned: <code class=highlight><span class=n>v</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>get</span><span class=o><</span><span class=n>T</span><span class=o>></span><span class=p>()</span></code>.</li> <li>For a type whose <code>from_json()</code> accepts views (see <a href=../get/ ><code>get<T>()</code></a>), that <code>from_json()</code> is called with the view and the existing <code>v</code>, without building a <code>BasicJsonType</code> value.</li> <li>For every other type, the subtree is built into a <code>BasicJsonType</code> value and <code class=highlight><span class=n>materialize</span><span class=p>().</span><span class=n>get_to</span><span class=p>(</span><span class=n>v</span><span class=p>)</span></code> is called, i.e. <code>from_json()</code> is invoked with the existing <code>v</code>, exactly as <a href=../../basic_json/get_to/ ><code>BasicJsonType::get_to()</code></a> does.</li> </ul> <h2 id=template-parameters>Template parameters<a class=headerlink href=#template-parameters title="Permanent link">¶</a></h2> <dl> <dt><code>T</code></dt> <dd>the type to convert the value to</dd> </dl> <h2 id=parameters>Parameters<a class=headerlink href=#parameters title="Permanent link">¶</a></h2> <dl> <dt><code>v</code> (out)</dt> <dd>the variable to store the converted value in</dd> </dl> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">¶</a></h2> <p><code>v</code>, allowing calls to chain</p> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">¶</a></h2> <ul> <li>For the directly converted types: strong exception safety. If an exception is thrown, <code>v</code> is not modified.</li> <li>For every other type: as for <a href=../../basic_json/get_to/ ><code>BasicJsonType::get_to()</code></a>. <code>materialize()</code> throws before <code>v</code> is touched, but a <code>from_json()</code> that throws may leave <code>v</code> partly modified.</li> </ul> <h2 id=exceptions>Exceptions<a class=headerlink href=#exceptions title="Permanent link">¶</a></h2> <ul> <li>For the directly converted types: whatever <a href=../get/ ><code>get<T>()</code></a> throws for the same value and <code>T</code>.</li> <li>For every other type: whatever <a href=../materialize/ ><code>materialize()</code></a> and <a href=../../basic_json/get_to/ ><code>BasicJsonType::get_to()</code></a> throw.</li> </ul> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">¶</a></h2> <ul> <li>For the directly converted types: whatever <a href=../get/ ><code>get<T>()</code></a> has for the same <code>T</code>.</li> <li>For every other type: that of <a href=../materialize/ ><code>materialize()</code></a>, plus that of <a href=../../basic_json/get_to/ ><code>BasicJsonType::get_to()</code></a>.</li> </ul> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">¶</a></h2> <p>The difference between the two ways matters for a <code>from_json()</code> that sets only the fields present in the <abbr title="JavaScript Object Notation">JSON</abbr>: since it runs on the existing <code>v</code>, the other fields of <code>v</code> keep their values, whereas assigning <code>get<T>()</code> would replace them with those of a default-constructed <code>T</code>.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">¶</a></h2> <details class=example> <summary>Example</summary> <p>The example below reads several fields of a service configuration directly into existing variables, then uses the returned reference to fold the <code class=highlight><span class=n>host</span></code>/<code class=highlight><span class=n>port</span></code> pair into a single string in the same expression.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><iostream></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json_view.hpp></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><string></span>
|
||||
|
||||
<span class=k>using</span><span class=w> </span><span class=n>json_document</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>json_view</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_view</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_view</span><span class=p>;</span>
|
||||
|
||||
<span class=kt>int</span><span class=w> </span><span class=nf>main</span><span class=p>()</span>
|
||||
<span class=p>{</span>
|
||||
@@ -30,4 +30,4 @@
|
||||
<span class=p>}</span>
|
||||
</code></pre></div> <p>Output:</p> <div class=highlight><pre><span></span><code><span class=err>db.example.com</span><span class=p>:</span><span class=mi>5432</span><span class=w> </span><span class=err>(</span><span class=kc>tls</span><span class=err>)</span>
|
||||
<span class=mi>14</span>
|
||||
</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">¶</a></h2> <ul> <li><a href=../get/ >get</a> - convert the value to a given type</li> <li><a href=../../basic_json/get_to/ ><code>BasicJsonType::get_to</code></a> - the corresponding function of <code>basic_json</code></li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">¶</a></h2> <ul> <li>Added in version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="October 21, 2026 08:21:27 UTC">October 21, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright © 2013-2026 Niels Lohmann </div> </div> <div class=md-social> <a href="https://github.com/nlohmann" target="_blank" rel="noopener" title="github.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 512 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><path d="M173.9 397.4c0 2-2.3 3.6-5.2 3.6-3.3.3-5.6-1.3-5.6-3.6 0-2 2.3-3.6 5.2-3.6 3-.3 5.6 1.3 5.6 3.6m-31.1-4.5c-.7 2 1.3 4.3 4.3 4.9 2.6 1 5.6 0 6.2-2s-1.3-4.3-4.3-5.2c-2.6-.7-5.5.3-6.2 2.3m44.2-1.7c-2.9.7-4.9 2.6-4.6 4.9.3 2 2.9 3.3 5.9 2.6 2.9-.7 4.9-2.6 4.6-4.6-.3-1.9-3-3.2-5.9-2.9M252.8 8C114.1 8 8 113.3 8 252c0 110.9 69.8 205.8 169.5 239.2 12.8 2.3 17.3-5.6 17.3-12.1 0-6.2-.3-40.4-.3-61.4 0 0-70 15-84.7-29.8 0 0-11.4-29.1-27.8-36.6 0 0-22.9-15.7 1.6-15.4 0 0 24.9 2 38.6 25.8 21.9 38.6 58.6 27.5 72.9 20.9 2.3-16 8.8-27.1 16-33.7-55.9-6.2-112.3-14.3-112.3-110.5 0-27.5 7.6-41.3 23.6-58.9-2.6-6.5-11.1-33.3 2.6-67.9 20.9-6.5 69 27 69 27 20-5.6 41.5-8.5 62.8-8.5s42.8 2.9 62.8 8.5c0 0 48.1-33.6 69-27 13.7 34.7 5.2 61.4 2.6 67.9 16 17.7 25.8 31.5 25.8 58.9 0 96.5-58.9 104.2-114.8 110.5 9.2 7.9 17 22.9 17 46.4 0 33.7-.3 75.4-.3 83.6 0 6.5 4.6 14.4 17.3 12.1C436.2 457.8 504 362.9 504 252 504 113.3 391.5 8 252.8 8M105.2 352.9c-1.3 1-1 3.3.7 5.2 1.6 1.6 3.9 2.3 5.2 1 1.3-1 1-3.3-.7-5.2-1.6-1.6-3.9-2.3-5.2-1m-10.8-8.1c-.7 1.3.3 2.9 2.3 3.9 1.6 1 3.6.7 4.3-.7.7-1.3-.3-2.9-2.3-3.9-2-.6-3.6-.3-4.3.7m32.4 35.6c-1.6 1.3-1 4.3 1.3 6.2 2.3 2.3 5.2 2.6 6.5 1 1.3-1.3.7-4.3-1.3-6.2-2.2-2.3-5.2-2.6-6.5-1m-11.4-14.7c-1.6 1-1.6 3.6 0 5.9s4.3 3.3 5.6 2.3c1.6-1.3 1.6-3.9 0-6.2-1.4-2.3-4-3.3-5.6-2"/></svg> </a> <a href="https://www.linkedin.com/in/nielslohmann/" target="_blank" rel="noopener" title="www.linkedin.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 448 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><path d="M416 32H31.9C14.3 32 0 46.5 0 64.3v383.4C0 465.5 14.3 480 31.9 480H416c17.6 0 32-14.5 32-32.3V64.3c0-17.8-14.4-32.3-32-32.3M135.4 416H69V202.2h66.5V416zM102.2 96a38.5 38.5 0 1 1 0 77 38.5 38.5 0 1 1 0-77m282.1 320h-66.4V312c0-24.8-.5-56.7-34.5-56.7-34.6 0-39.9 27-39.9 54.9V416h-66.4V202.2h63.7v29.2h.9c8.9-16.8 30.6-34.5 62.9-34.5 67.2 0 79.7 44.3 79.7 101.9z"/></svg> </a> <a href="https://www.xing.com/profile/Niels_Lohmann" target="_blank" rel="noopener" title="www.xing.com" class=Line truncated
|
||||
</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">¶</a></h2> <ul> <li><a href=../get/ >get</a> - convert the value to a given type</li> <li><a href=../../basic_json/get_to/ ><code>BasicJsonType::get_to</code></a> - the corresponding function of <code>basic_json</code></li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">¶</a></h2> <ul> <li>Added in version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="October 26, 2026 19:13:31 UTC">October 26, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright © 2013-2026 Niels Lohmann </div> </div> <div class=md-social> <a href="https://github.com/nlohmann" target="_blank" rel="noopener" title="github.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 512 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><path d="M173.9 397.4c0 2-2.3 3.6-5.2 3.6-3.3.3-5.6-1.3-5.6-3.6 0-2 2.3-3.6 5.2-3.6 3-.3 5.6 1.3 5.6 3.6m-31.1-4.5c-.7 2 1.3 4.3 4.3 4.9 2.6 1 5.6 0 6.2-2s-1.3-4.3-4.3-5.2c-2.6-.7-5.5.3-6.2 2.3m44.2-1.7c-2.9.7-4.9 2.6-4.6 4.9.3 2 2.9 3.3 5.9 2.6 2.9-.7 4.9-2.6 4.6-4.6-.3-1.9-3-3.2-5.9-2.9M252.8 8C114.1 8 8 113.3 8 252c0 110.9 69.8 205.8 169.5 239.2 12.8 2.3 17.3-5.6 17.3-12.1 0-6.2-.3-40.4-.3-61.4 0 0-70 15-84.7-29.8 0 0-11.4-29.1-27.8-36.6 0 0-22.9-15.7 1.6-15.4 0 0 24.9 2 38.6 25.8 21.9 38.6 58.6 27.5 72.9 20.9 2.3-16 8.8-27.1 16-33.7-55.9-6.2-112.3-14.3-112.3-110.5 0-27.5 7.6-41.3 23.6-58.9-2.6-6.5-11.1-33.3 2.6-67.9 20.9-6.5 69 27 69 27 20-5.6 41.5-8.5 62.8-8.5s42.8 2.9 62.8 8.5c0 0 48.1-33.6 69-27 13.7 34.7 5.2 61.4 2.6 67.9 16 17.7 25.8 31.5 25.8 58.9 0 96.5-58.9 104.2-114.8 110.5 9.2 7.9 17 22.9 17 46.4 0 33.7-.3 75.4-.3 83.6 0 6.5 4.6 14.4 17.3 12.1C436.2 457.8 504 362.9 504 252 504 113.3 391.5 8 252.8 8M105.2 352.9c-1.3 1-1 3.3.7 5.2 1.6 1.6 3.9 2.3 5.2 1 1.3-1 1-3.3-.7-5.2-1.6-1.6-3.9-2.3-5.2-1m-10.8-8.1c-.7 1.3.3 2.9 2.3 3.9 1.6 1 3.6.7 4.3-.7.7-1.3-.3-2.9-2.3-3.9-2-.6-3.6-.3-4.3.7m32.4 35.6c-1.6 1.3-1 4.3 1.3 6.2 2.3 2.3 5.2 2.6 6.5 1 1.3-1.3.7-4.3-1.3-6.2-2.2-2.3-5.2-2.6-6.5-1m-11.4-14.7c-1.6 1-1.6 3.6 0 5.9s4.3 3.3 5.6 2.3c1.6-1.3 1.6-3.9 0-6.2-1.4-2.3-4-3.3-5.6-2"/></svg> </a> <a href="https://www.linkedin.com/in/nielslohmann/" target="_blank" rel="noopener" title="www.linkedin.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 448 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><path d="M416 32H31.9C14.3 32 0 46.5 0 64.3v383.4C0 465.5 14.3 480 31.9 480H416c17.6 0 32-14.5 32-32.3V64.3c0-17.8-14.4-32.3-32-32.3M135.4 416H69V202.2h66.5V416zM102.2 96a38.5 38.5 0 1 1 0 77 38.5 38.5 0 1 1 0-77m282.1 320h-66.4V312c0-24.8-.5-56.7-34.5-56.7-34.6 0-39.9 27-39.9 54.9V416h-66.4V202.2h63.7v29.2h.9c8.9-16.8 30.6-34.5 62.9-34.5 67.2 0 79.7 44.3 79.7 101.9z"/></svg> </a> <a href="https://www.xing.com/profile/Niels_Lohmann" target="_blank" rel="noopener" title="www.xing.com" class=Line truncated
|
||||
@@ -5,9 +5,10 @@ template<typename T>
|
||||
T& get_to(T& v) const;
|
||||
```
|
||||
|
||||
Converts the value to `T` and stores it in `v`, in one of two ways:
|
||||
Converts the value to `T` and stores it in `v`, in one of three ways:
|
||||
|
||||
- For the types that [`get<T>()`](https://json.nlohmann.me/api/basic_json_view/get/index.md) converts directly -- arithmetic types, `bool`, `std::nullptr_t`, [`string_view_t`](https://json.nlohmann.me/api/basic_json_view/#member-types), `std::basic_string`, `BasicJsonType`, `basic_json_view`, `std::vector`, and `std::map`/`std::unordered_map` with string keys -- `v` is assigned: `v = get<T>()`.
|
||||
- For the types that [`get<T>()`](https://json.nlohmann.me/api/basic_json_view/get/index.md) converts directly -- arithmetic types, `bool`, `std::nullptr_t`, [`string_view_t`](https://json.nlohmann.me/api/basic_json_view/#member-types), `std::basic_string`, `BasicJsonType`, `basic_json_view`, vectors of these, and maps of views -- `v` is assigned: `v = get<T>()`.
|
||||
- For a type whose `from_json()` accepts views (see [`get<T>()`](https://json.nlohmann.me/api/basic_json_view/get/index.md)), that `from_json()` is called with the view and the existing `v`, without building a `BasicJsonType` value.
|
||||
- For every other type, the subtree is built into a `BasicJsonType` value and `materialize().get_to(v)` is called, i.e. `from_json()` is invoked with the existing `v`, exactly as [`BasicJsonType::get_to()`](https://json.nlohmann.me/api/basic_json/get_to/index.md) does.
|
||||
|
||||
## Template parameters
|
||||
@@ -52,8 +53,8 @@ The example below reads several fields of a service configuration directly into
|
||||
#include <nlohmann/json_view.hpp>
|
||||
#include <string>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using json_view = nlohmann::json_view;
|
||||
using nlohmann::json_document;
|
||||
using nlohmann::json_view;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -1,3 +1,3 @@
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/" rel="canonical"><link href=../basic_json_document/source/ rel=prev><link href=basic_json_view/ rel=next><link rel=icon href=../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>Overview - JSON for Modern C++</title><link rel=stylesheet href=../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../css/custom.css><script>__md_scope=new URL("../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#nlohmannbasic_json_view class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> Overview </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5"/></svg> </laLine truncated
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/" rel="canonical"><link href=../basic_json_document/source/ rel=prev><link href=basic_json_view/ rel=next><link rel=icon href=../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>Overview - JSON for Modern C++</title><link rel=stylesheet href=../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../css/custom.css><script>__md_scope=new URL("../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#nlohmannbasic_json_view class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> Overview </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5"/></svg> </laLine truncated
|
||||
<span class=k>class</span><span class=w> </span><span class=nc>basic_json_view</span><span class=p>;</span>
|
||||
</code></pre></div> <p>A read-only handle to one value of a <a href=../basic_json_document/ ><code>basic_json_document</code></a>: two pointers (a pointer to the document and a pointer into its index), trivially copyable. A view is valid as long as</p> <ul> <li>the document is alive,</li> <li>the document has not been re-parsed with <a href=../basic_json_document/read/ ><code>read()</code></a> (or <a href=../basic_json_document/parse/ ><code>parse()</code></a> into it) or shrunk with <a href=../basic_json_document/shrink_to_fit/ ><code>shrink_to_fit()</code></a> since the view was taken, and</li> <li>if the document borrows its source text, that text is still alive and unmodified (floating-point values and unescaped strings are read from it lazily).</li> </ul> <p>Moving the document itself does not invalidate its views: the index is heap-allocated independently of the <code>basic_json_document</code> object.</p> <p><code>basic_json_view</code> provides the read-only part of the <code>BasicJsonType</code> interface:</p> <ul> <li>the type-inspection functions</li> <li>element access</li> <li>lookup</li> <li>iteration</li> <li>conversion: <a href=get/ ><code>get<T>()</code></a>, <a href=get_string/ ><code>get_string()</code></a>, <a href=number_token/ ><code>number_token()</code></a>, and <a href=materialize/ ><code>materialize()</code></a> to build the <code>BasicJsonType</code> value of a subtree on demand</li> <li>comparison: <a href=operator_eq/ ><code>operator==</code></a> and <a href=operator_ne/ ><code>operator!=</code></a> compare two views, or a view and a <code>BasicJsonType</code> value, without ever building a <code>BasicJsonType</code> value for a view; no ordering comparison (<code class=highlight><span class=k>operator</span><span class=o><</span></code>) is provided</li> </ul> <p><a href=operator%5B%5D/ ><code>operator[]</code></a>, <a href=at/ ><code>at</code></a>, <a href=contains/ ><code>contains</code></a>, and <a href=value/ ><code>value</code></a> also accept a <a href=../json_pointer/ ><code>json_pointer</code></a>. Unlike <code>basic_json</code>, there are no implicit conversion operators (no <code class=highlight><span class=k>operator</span><span class=w> </span><span class=n>ValueType</span><span class=p>()</span></code>), and no <code class=highlight><span class=n>get_ptr</span><span class=p>()</span></code> or <code class=highlight><span class=n>get_ref</span><span class=p>()</span></code>; see <a href=get/ ><code>get</code></a>.</p> <p><code>basic_json_view</code> itself is always read-only -- it never has a <code>set</code> or <code>push_back</code> of its own. A view of an <strong>editable</strong> document (<code class=highlight><span class=n>Editable</span><span class=w> </span><span class=o>==</span><span class=w> </span><span class=nb>true</span></code>) sees every edit made through <a href=../basic_json_document/set/ ><code>basic_json_document::set</code></a> and <a href=../basic_json_document/push_back/ ><code>basic_json_document::push_back</code></a>: once a value is changed, every view that still refers to it -- including ones taken before the change -- reads the new value. See <a href=../basic_json_document/#edits>Edits</a>.</p> <h2 id=template-parameters>Template parameters<a class=headerlink href=#template-parameters title="Permanent link">¶</a></h2> <dl> <dt><code>BasicJsonType</code></dt> <dd>a specialization of <a href=../basic_json/ ><code>basic_json</code></a>, matching the <a href=../basic_json_document/ ><code>basic_json_document</code></a> the view was taken from.</dd> <dt><code>Editable</code></dt> <dd>whether the view is of an editable document, matching the <a href=../basic_json_document/ ><code>basic_json_document</code></a> it was taken from (optional, <code class=highlight><span class=nb>false</span></code> by default). See <a href=../basic_json_document/#edits>Edits</a>.</dd> </dl> <h2 id=specializations>Specializations<a class=headerlink href=#specializations title="Permanent link">¶</a></h2> <ul> <li><a href=../json_view/ ><strong>json_view</strong></a> - views of a <a href=../json_document/ ><code>json_document</code></a></li> <li><a href=../ordered_json_view/ ><strong>ordered_json_view</strong></a> - views of an <a href=../ordered_json_document/ ><code>ordered_json_document</code></a></li> <li><a href=../json_editable_view/ ><strong>json_editable_view</strong></a> - views of a <a href=../json_editable_document/ ><code>json_editable_document</code></a></li> <li><a href=../ordered_json_editable_view/ ><strong>ordered_json_editable_view</strong></a> - views of an <a href=../ordered_json_editable_document/ ><code>ordered_json_editable_document</code></a></li> </ul> <h2 id=member-types>Member types<a class=headerlink href=#member-types title="Permanent link">¶</a></h2> <ul> <li><strong>value_t</strong> - the <abbr title="JavaScript Object Notation">JSON</abbr> type enumeration, see <a href=../basic_json/value_t/ ><code>basic_jsonLine truncated
|
||||
</code></pre></div> <p>A read-only handle to one value of a <a href=../basic_json_document/ ><code>basic_json_document</code></a>: two pointers (a pointer to the document and a pointer into its index), trivially copyable. A view is valid as long as</p> <ul> <li>the document is alive,</li> <li>the document has not been re-parsed with <a href=../basic_json_document/read/ ><code>read()</code></a> (or <a href=../basic_json_document/parse/ ><code>parse()</code></a> into it) or shrunk with <a href=../basic_json_document/shrink_to_fit/ ><code>shrink_to_fit()</code></a> since the view was taken, and</li> <li>if the document borrows its source text, that text is still alive and unmodified (floating-point values and unescaped strings are read from it lazily).</li> </ul> <p>Moving the document itself does not invalidate its views: the index is heap-allocated independently of the <code>basic_json_document</code> object.</p> <p><code>basic_json_view</code> provides the read-only part of the <code>BasicJsonType</code> interface:</p> <ul> <li>the type-inspection functions</li> <li>element access</li> <li>lookup</li> <li>iteration</li> <li>conversion: <a href=get/ ><code>get<T>()</code></a>, <a href=get_string/ ><code>get_string()</code></a>, <a href=number_token/ ><code>number_token()</code></a>, and <a href=materialize/ ><code>materialize()</code></a> to build the <code>BasicJsonType</code> value of a subtree on demand</li> <li>comparison: <a href=operator_eq/ ><code>operator==</code></a> and <a href=operator_ne/ ><code>operator!=</code></a> compare two views, or a view and a <code>BasicJsonType</code> value, without ever building a <code>BasicJsonType</code> value for a view; no ordering comparison (<code class=highlight><span class=k>operator</span><span class=o><</span></code>) is provided</li> </ul> <p><a href=operator%5B%5D/ ><code>operator[]</code></a>, <a href=at/ ><code>at</code></a>, <a href=contains/ ><code>contains</code></a>, and <a href=value/ ><code>value</code></a> also accept a <a href=../json_pointer/ ><code>json_pointer</code></a>. Unlike <code>basic_json</code>, there are no implicit conversion operators (no <code class=highlight><span class=k>operator</span><span class=w> </span><span class=n>ValueType</span><span class=p>()</span></code>), and no <code class=highlight><span class=n>get_ptr</span><span class=p>()</span></code> or <code class=highlight><span class=n>get_ref</span><span class=p>()</span></code>; see <a href=get/ ><code>get</code></a>.</p> <p><code>basic_json_view</code> itself is always read-only -- it never has a <code>set</code> or <code>push_back</code> of its own. A view of an <strong>editable</strong> document (<code class=highlight><span class=n>view_mode</span><span class=o>::</span><span class=n>editable</span></code>) sees every edit made through <a href=../basic_json_document/set/ ><code>basic_json_document::set</code></a> and <a href=../basic_json_document/push_back/ ><code>basic_json_document::push_back</code></a>: once a value is changed, every view that still refers to it -- including ones taken before the change -- reads the new value. See <a href=../basic_json_document/#edits>Edits</a>.</p> <h2 id=template-parameters>Template parameters<a class=headerlink href=#template-parameters title="Permanent link">¶</a></h2> <dl> <dt><code>BasicJsonType</code></dt> <dd>a specialization of <a href=../basic_json/ ><code>basic_json</code></a>, matching the <a href=../basic_json_document/ ><code>basic_json_document</code></a> the view was taken from.</dd> <dt><code>Mode</code></dt> <dd>a <a href=../view_mode/ ><code>view_mode</code></a>: whether the view is of an editable document, matching the <a href=../basic_json_document/ ><code>basic_json_document</code></a> it was taken from (optional, <code class=highlight><span class=n>view_mode</span><span class=o>::</span><span class=n>read_only</span></code> by default). See <a href=../basic_json_document/#edits>Edits</a>.</dd> </dl> <h2 id=specializations>Specializations<a class=headerlink href=#specializations title="Permanent link">¶</a></h2> <ul> <li><a href=../json_view/ ><strong>json_view</strong></a> - views of a <a href=../json_document/ ><code>json_document</code></a></li> <li><a href=../ordered_json_view/ ><strong>ordered_json_view</strong></a> - views of an <a href=../ordered_json_document/ ><code>ordered_json_document</code></a></li> <li><a href=../json_editable_view/ ><strong>json_editable_view</strong></a> - views of a <a href=../json_editable_document/ ><code>json_editable_document</code></a></li> <li><a href=../ordered_json_editable_view/ ><strong>ordered_json_editable_view</strong></a> - views of an <a href=../ordered_json_editable_document/ ><code>ordered_json_editable_document</code></a></li> </ul> <h2 id=member-types>Member types<a class=headerlink href=#member-types title="Permanent link">¶</a></h2> <ul> <li><strong>basic_json_type</strong> - <code>BasicJsonType</code> (it also marks the class foLine truncated
|
||||
@@ -3,7 +3,7 @@
|
||||
Defined in header `<nlohmann/json_view.hpp>`
|
||||
|
||||
```
|
||||
template<typename BasicJsonType, bool Editable = false>
|
||||
template<typename BasicJsonType, view_mode Mode = view_mode::read_only>
|
||||
class basic_json_view;
|
||||
```
|
||||
|
||||
@@ -26,13 +26,13 @@ Moving the document itself does not invalidate its views: the index is heap-allo
|
||||
|
||||
[`operator[]`](https://json.nlohmann.me/api/basic_json_view/operator%5B%5D/index.md), [`at`](https://json.nlohmann.me/api/basic_json_view/at/index.md), [`contains`](https://json.nlohmann.me/api/basic_json_view/contains/index.md), and [`value`](https://json.nlohmann.me/api/basic_json_view/value/index.md) also accept a [`json_pointer`](https://json.nlohmann.me/api/json_pointer/index.md). Unlike `basic_json`, there are no implicit conversion operators (no `operator ValueType()`), and no `get_ptr()` or `get_ref()`; see [`get`](https://json.nlohmann.me/api/basic_json_view/get/index.md).
|
||||
|
||||
`basic_json_view` itself is always read-only -- it never has a `set` or `push_back` of its own. A view of an **editable** document (`Editable == true`) sees every edit made through [`basic_json_document::set`](https://json.nlohmann.me/api/basic_json_document/set/index.md) and [`basic_json_document::push_back`](https://json.nlohmann.me/api/basic_json_document/push_back/index.md): once a value is changed, every view that still refers to it -- including ones taken before the change -- reads the new value. See [Edits](https://json.nlohmann.me/api/basic_json_document/#edits).
|
||||
`basic_json_view` itself is always read-only -- it never has a `set` or `push_back` of its own. A view of an **editable** document (`view_mode::editable`) sees every edit made through [`basic_json_document::set`](https://json.nlohmann.me/api/basic_json_document/set/index.md) and [`basic_json_document::push_back`](https://json.nlohmann.me/api/basic_json_document/push_back/index.md): once a value is changed, every view that still refers to it -- including ones taken before the change -- reads the new value. See [Edits](https://json.nlohmann.me/api/basic_json_document/#edits).
|
||||
|
||||
## Template parameters
|
||||
|
||||
`BasicJsonType` : a specialization of [`basic_json`](https://json.nlohmann.me/api/basic_json/index.md), matching the [`basic_json_document`](https://json.nlohmann.me/api/basic_json_document/index.md) the view was taken from.
|
||||
|
||||
`Editable` : whether the view is of an editable document, matching the [`basic_json_document`](https://json.nlohmann.me/api/basic_json_document/index.md) it was taken from (optional, `false` by default). See [Edits](https://json.nlohmann.me/api/basic_json_document/#edits).
|
||||
`Mode` : a [`view_mode`](https://json.nlohmann.me/api/view_mode/index.md): whether the view is of an editable document, matching the [`basic_json_document`](https://json.nlohmann.me/api/basic_json_document/index.md) it was taken from (optional, `view_mode::read_only` by default). See [Edits](https://json.nlohmann.me/api/basic_json_document/#edits).
|
||||
|
||||
## Specializations
|
||||
|
||||
@@ -43,6 +43,7 @@ Moving the document itself does not invalidate its views: the index is heap-allo
|
||||
|
||||
## Member types
|
||||
|
||||
- **basic_json_type** - `BasicJsonType` (it also marks the class for [`is_json_view`](https://json.nlohmann.me/api/is_json_view/index.md))
|
||||
- **value_t** - the JSON type enumeration, see [`basic_json::value_t`](https://json.nlohmann.me/api/basic_json/value_t/index.md)
|
||||
- **string_t**, **number_integer_t**, **number_unsigned_t**, **number_float_t**, **json_pointer** - the corresponding member types of `BasicJsonType`
|
||||
- **size_type** - `std::size_t`
|
||||
|
||||
@@ -29,7 +29,7 @@ Constant.
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -1,8 +1,8 @@
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/is_array/" rel="canonical"><link href=../get_to/ rel=prev><link href=../is_binary/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>is_array - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#nlohmannbasic_json_viewis_array class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> is_array </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 Line truncated
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/is_array/" rel="canonical"><link href=../get_to/ rel=prev><link href=../is_binary/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>is_array - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#nlohmannbasic_json_viewis_array class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> is_array </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 Line truncated
|
||||
</code></pre></div> <p>This function returns <code class=highlight><span class=nb>true</span></code> if and only if the value is an array.</p> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">¶</a></h2> <p><code class=highlight><span class=nb>true</span></code> if the type is an array, <code class=highlight><span class=nb>false</span></code> otherwise.</p> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">¶</a></h2> <p>No-throw guarantee: this function never throws exceptions.</p> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">¶</a></h2> <p>Constant.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">¶</a></h2> <details class=example> <summary>Example</summary> <p>The example below classifies several parsed documents by the type of their root value, without materializing any of them into a <code>BasicJsonType</code> value.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><iostream></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json_view.hpp></span>
|
||||
|
||||
<span class=k>using</span><span class=w> </span><span class=n>json_document</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
|
||||
<span class=kt>int</span><span class=w> </span><span class=nf>main</span><span class=p>()</span>
|
||||
<span class=p>{</span>
|
||||
|
||||
@@ -28,7 +28,7 @@ The example below classifies several parsed documents by the type of their root
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -31,7 +31,7 @@ Constant.
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -1,8 +1,8 @@
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/is_binary/" rel="canonical"><link href=../is_array/ rel=prev><link href=../is_boolean/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>is_binary - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#nlohmannbasic_json_viewis_binary class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> is_binary </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12Line truncated
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/is_binary/" rel="canonical"><link href=../is_array/ rel=prev><link href=../is_boolean/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>is_binary - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#nlohmannbasic_json_viewis_binary class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> is_binary </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12Line truncated
|
||||
</code></pre></div> <p>This function always returns <code class=highlight><span class=nb>false</span></code>: a document is only ever parsed from <abbr title="JavaScript Object Notation">JSON</abbr> text, never from <abbr title="Concise Binary Object Representation">CBOR</abbr> or the other binary formats, and a <abbr title="JavaScript Object Notation">JSON</abbr> text has no binary values, so a view can never refer to one. The function exists for interface parity with <a href=../../basic_json/is_binary/ ><code>BasicJsonType::is_binary</code></a>.</p> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">¶</a></h2> <p><code class=highlight><span class=nb>false</span></code>, always.</p> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">¶</a></h2> <p>No-throw guarantee: this function never throws exceptions.</p> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">¶</a></h2> <p>Constant.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">¶</a></h2> <details class=example> <summary>Example</summary> <p>The example below classifies several parsed documents by the type of their root value, without materializing any of them into a <code>BasicJsonType</code> value.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><iostream></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json_view.hpp></span>
|
||||
|
||||
<span class=k>using</span><span class=w> </span><span class=n>json_document</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
|
||||
<span class=kt>int</span><span class=w> </span><span class=nf>main</span><span class=p>()</span>
|
||||
<span class=p>{</span>
|
||||
|
||||
@@ -28,7 +28,7 @@ The example below classifies several parsed documents by the type of their root
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -29,7 +29,7 @@ Constant.
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -1,8 +1,8 @@
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/is_boolean/" rel="canonical"><link href=../is_binary/ rel=prev><link href=../is_discarded/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>is_boolean - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> is_boolean </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark 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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/is_boolean/" rel="canonical"><link href=../is_binary/ rel=prev><link href=../is_discarded/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>is_boolean - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> is_boolean </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark 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4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 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|
||||
</code></pre></div> <p>This function returns <code class=highlight><span class=nb>true</span></code> if and only if the value is a boolean.</p> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">¶</a></h2> <p><code class=highlight><span class=nb>true</span></code> if the type is a boolean, <code class=highlight><span class=nb>false</span></code> otherwise.</p> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">¶</a></h2> <p>No-throw guarantee: this function never throws exceptions.</p> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">¶</a></h2> <p>Constant.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">¶</a></h2> <details class=example> <summary>Example</summary> <p>The example below classifies several parsed documents by the type of their root value, without materializing any of them into a <code>BasicJsonType</code> value.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><iostream></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json_view.hpp></span>
|
||||
|
||||
<span class=k>using</span><span class=w> </span><span class=n>json_document</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
|
||||
<span class=kt>int</span><span class=w> </span><span class=nf>main</span><span class=p>()</span>
|
||||
<span class=p>{</span>
|
||||
|
||||
@@ -28,7 +28,7 @@ The example below classifies several parsed documents by the type of their root
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -42,7 +42,7 @@ A `basic_json_view` is not convertible to `#!cpp bool`: such a conversion would
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -1,8 +1,8 @@
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/is_discarded/" rel="canonical"><link href=../is_boolean/ rel=prev><link href=../is_null/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>is_discarded - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> is_discarded </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to 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4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/is_discarded/" rel="canonical"><link href=../is_boolean/ rel=prev><link href=../is_null/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>is_discarded - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#nlohmannbasic_json_viewis_discarded class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> is_discarded </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 1Line truncated
|
||||
</code></pre></div> <p>Returns whether this view is invalid, i.e. does not refer to a value. This is the case for a default-constructed view (see <a href=../basic_json_view/ >(constructor)</a>), and for <a href=../../basic_json_document/root/ ><code>root()</code></a> of a document that is itself <a href=../../basic_json_document/is_discarded/ >discarded</a> -- in particular, the root of a failed <a href=../../basic_json_document/parse/ ><code>parse()</code></a> with <code>allow_exceptions</code> set to <code class=highlight><span class=nb>false</span></code>.</p> <p>A discarded view is also what <a href=../operator%5B%5D/ ><code>operator[]</code></a> returns for a missing key, an index out of range, or a <abbr title="JavaScript Object Notation">JSON</abbr> pointer that cannot be resolved, and for any access on a view that is itself discarded (so a chain such as <code class=highlight><span class=n>v</span><span class=p>[</span><span class=s>"a"</span><span class=p>][</span><span class=s>"b"</span><span class=p>]</span></code> is safe). <a href=../at/ ><code>at</code></a> throws instead.</p> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">¶</a></h2> <p><code class=highlight><span class=nb>true</span></code> if the view or its document is discarded, <code class=highlight><span class=nb>false</span></code> otherwise.</p> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">¶</a></h2> <p>No-throw guarantee: this function never throws exceptions.</p> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">¶</a></h2> <p>Constant.</p> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">¶</a></h2> <p>A <code>basic_json_view</code> is not convertible to <code class=highlight><span class=kt>bool</span></code>: such a conversion would mean "refers to a value", whereas <code>basic_json</code> converts to the <code class=highlight><span class=kt>bool</span></code> it holds, so the same code would silently behave differently. Test <code class=highlight><span class=o>!</span><span class=n>v</span><span class=p>.</span><span class=n>is_discarded</span><span class=p>()</span></code> explicitly.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">¶</a></h2> <details class=example> <summary>Example</summary> <p>The example below classifies several parsed documents by the type of their root value, without materializing any of them into a <code>BasicJsonType</code> value.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><iostream></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json_view.hpp></span>
|
||||
|
||||
<span class=k>using</span><span class=w> </span><span class=n>json_document</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
|
||||
<span class=kt>int</span><span class=w> </span><span class=nf>main</span><span class=p>()</span>
|
||||
<span class=p>{</span>
|
||||
|
||||
@@ -34,7 +34,7 @@ The example below classifies several parsed documents by the type of their root
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -29,7 +29,7 @@ Constant.
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -1,8 +1,8 @@
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/is_null/" rel="canonical"><link href=../is_discarded/ rel=prev><link href=../is_number/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>is_null - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#nlohmannbasic_json_viewis_null class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> is_null </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.Line truncated
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/is_null/" rel="canonical"><link href=../is_discarded/ rel=prev><link href=../is_number/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>is_null - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#nlohmannbasic_json_viewis_null class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> is_null </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.Line truncated
|
||||
</code></pre></div> <p>This function returns <code class=highlight><span class=nb>true</span></code> if and only if the value is <code class=highlight><span class=kc>null</span></code>.</p> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">¶</a></h2> <p><code class=highlight><span class=nb>true</span></code> if the type is <code class=highlight><span class=kc>null</span></code>, <code class=highlight><span class=nb>false</span></code> otherwise.</p> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">¶</a></h2> <p>No-throw guarantee: this function never throws exceptions.</p> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">¶</a></h2> <p>Constant.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">¶</a></h2> <details class=example> <summary>Example</summary> <p>The example below classifies several parsed documents by the type of their root value, without materializing any of them into a <code>BasicJsonType</code> value.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><iostream></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json_view.hpp></span>
|
||||
|
||||
<span class=k>using</span><span class=w> </span><span class=n>json_document</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
|
||||
<span class=kt>int</span><span class=w> </span><span class=nf>main</span><span class=p>()</span>
|
||||
<span class=p>{</span>
|
||||
|
||||
@@ -28,7 +28,7 @@ The example below classifies several parsed documents by the type of their root
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -29,7 +29,7 @@ Constant.
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -1,8 +1,8 @@
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/is_number/" rel="canonical"><link href=../is_null/ rel=prev><link href=../is_number_float/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>is_number - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> is_number </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark 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4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/is_number/" rel="canonical"><link href=../is_null/ rel=prev><link href=../is_number_float/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>is_number - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> is_number </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark 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4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.Line truncated
|
||||
</code></pre></div> <p>This function returns <code class=highlight><span class=nb>true</span></code> if and only if the value is a number, i.e. an integer, unsigned integer, or floating-point value. It is defined as <code class=highlight><span class=n>is_number_integer</span><span class=p>()</span><span class=w> </span><span class=o>||</span><span class=w> </span><span class=n>is_number_float</span><span class=p>()</span></code>.</p> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">¶</a></h2> <p><code class=highlight><span class=nb>true</span></code> if the type is a number, <code class=highlight><span class=nb>false</span></code> otherwise.</p> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">¶</a></h2> <p>No-throw guarantee: this function never throws exceptions.</p> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">¶</a></h2> <p>Constant.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">¶</a></h2> <details class=example> <summary>Example</summary> <p>The example below classifies several parsed documents by the type of their root value, without materializing any of them into a <code>BasicJsonType</code> value.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><iostream></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json_view.hpp></span>
|
||||
|
||||
<span class=k>using</span><span class=w> </span><span class=n>json_document</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
|
||||
<span class=kt>int</span><span class=w> </span><span class=nf>main</span><span class=p>()</span>
|
||||
<span class=p>{</span>
|
||||
|
||||
@@ -28,7 +28,7 @@ The example below classifies several parsed documents by the type of their root
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -35,7 +35,7 @@ integer-looking token in the source text.
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -1,8 +1,8 @@
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/is_number_float/" rel="canonical"><link href=../is_number/ rel=prev><link href=../is_number_integer/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>is_number_float - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> is_number_float </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5Line truncated
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/is_number_float/" rel="canonical"><link href=../is_number/ rel=prev><link href=../is_number_integer/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>is_number_float - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#nlohmannbasic_json_viewis_number_float class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> is_number_float </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5Line truncated
|
||||
</code></pre></div> <p>This function returns <code class=highlight><span class=nb>true</span></code> if and only if the value is a floating-point number.</p> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">¶</a></h2> <p><code class=highlight><span class=nb>true</span></code> if the type is <code class=highlight><span class=n>value_t</span><span class=o>::</span><span class=n>number_float</span></code>, <code class=highlight><span class=nb>false</span></code> otherwise.</p> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">¶</a></h2> <p>No-throw guarantee: this function never throws exceptions.</p> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">¶</a></h2> <p>Constant.</p> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">¶</a></h2> <p>As for <a href=../../basic_json/parse/ ><code>BasicJsonType::parse</code></a>, an integer literal that does not fit into the 64-bit integer type is classified as a floating-point number, so <code>is_number_float()</code> can be <code class=highlight><span class=nb>true</span></code> even for an integer-looking token in the source text.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">¶</a></h2> <details class=example> <summary>Example</summary> <p>The example below classifies several parsed documents by the type of their root value, without materializing any of them into a <code>BasicJsonType</code> value.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><iostream></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json_view.hpp></span>
|
||||
|
||||
<span class=k>using</span><span class=w> </span><span class=n>json_document</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
|
||||
<span class=kt>int</span><span class=w> </span><span class=nf>main</span><span class=p>()</span>
|
||||
<span class=p>{</span>
|
||||
|
||||
@@ -32,7 +32,7 @@ The example below classifies several parsed documents by the type of their root
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -34,7 +34,7 @@ values; use [`is_number_unsigned`](is_number_unsigned.md) to test for those spec
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -1,8 +1,8 @@
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/is_number_integer/" rel="canonical"><link href=../is_number_float/ rel=prev><link href=../is_number_unsigned/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>is_number_integer - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#nlohmannbasic_json_viewis_number_integer class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> is_number_integer </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 Line truncated
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/is_number_integer/" rel="canonical"><link href=../is_number_float/ rel=prev><link href=../is_number_unsigned/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>is_number_integer - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#nlohmannbasic_json_viewis_number_integer class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> is_number_integer </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 Line truncated
|
||||
</code></pre></div> <p>This function returns <code class=highlight><span class=nb>true</span></code> if and only if the value is an integer or unsigned integer number.</p> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">¶</a></h2> <p><code class=highlight><span class=nb>true</span></code> if the type is <code class=highlight><span class=n>value_t</span><span class=o>::</span><span class=n>number_integer</span></code> or <code class=highlight><span class=n>value_t</span><span class=o>::</span><span class=n>number_unsigned</span></code>, <code class=highlight><span class=nb>false</span></code> otherwise.</p> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">¶</a></h2> <p>No-throw guarantee: this function never throws exceptions.</p> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">¶</a></h2> <p>Constant.</p> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">¶</a></h2> <p>As for <a href=../../basic_json/is_number_integer/ ><code>BasicJsonType::is_number_integer</code></a>, this includes unsigned integer values; use <a href=../is_number_unsigned/ ><code>is_number_unsigned</code></a> to test for those specifically.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">¶</a></h2> <details class=example> <summary>Example</summary> <p>The example below classifies several parsed documents by the type of their root value, without materializing any of them into a <code>BasicJsonType</code> value.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><iostream></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json_view.hpp></span>
|
||||
|
||||
<span class=k>using</span><span class=w> </span><span class=n>json_document</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
|
||||
<span class=kt>int</span><span class=w> </span><span class=nf>main</span><span class=p>()</span>
|
||||
<span class=p>{</span>
|
||||
|
||||
@@ -32,7 +32,7 @@ The example below classifies several parsed documents by the type of their root
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -29,7 +29,7 @@ Constant.
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -1,8 +1,8 @@
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/is_number_unsigned/" rel="canonical"><link href=../is_number_integer/ rel=prev><link href=../is_object/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>is_number_unsigned - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> is_number_unsigned </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch 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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/is_number_unsigned/" rel="canonical"><link href=../is_number_integer/ rel=prev><link href=../is_object/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>is_number_unsigned - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> is_number_unsigned </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch 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4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 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|
||||
</code></pre></div> <p>This function returns <code class=highlight><span class=nb>true</span></code> if and only if the value is an unsigned integer number.</p> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">¶</a></h2> <p><code class=highlight><span class=nb>true</span></code> if the type is <code class=highlight><span class=n>value_t</span><span class=o>::</span><span class=n>number_unsigned</span></code>, <code class=highlight><span class=nb>false</span></code> otherwise.</p> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">¶</a></h2> <p>No-throw guarantee: this function never throws exceptions.</p> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">¶</a></h2> <p>Constant.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">¶</a></h2> <details class=example> <summary>Example</summary> <p>The example below classifies several parsed documents by the type of their root value, without materializing any of them into a <code>BasicJsonType</code> value.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><iostream></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json_view.hpp></span>
|
||||
|
||||
<span class=k>using</span><span class=w> </span><span class=n>json_document</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
|
||||
<span class=kt>int</span><span class=w> </span><span class=nf>main</span><span class=p>()</span>
|
||||
<span class=p>{</span>
|
||||
|
||||
@@ -28,7 +28,7 @@ The example below classifies several parsed documents by the type of their root
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -29,7 +29,7 @@ Constant.
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -1,8 +1,8 @@
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/is_object/" rel="canonical"><link href=../is_number_unsigned/ rel=prev><link href=../is_primitive/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>is_object - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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|
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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/is_object/" rel="canonical"><link href=../is_number_unsigned/ rel=prev><link href=../is_primitive/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>is_object - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#nlohmannbasic_json_viewis_object class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> is_object </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 Line truncated
|
||||
</code></pre></div> <p>This function returns <code class=highlight><span class=nb>true</span></code> if and only if the value is an object.</p> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">¶</a></h2> <p><code class=highlight><span class=nb>true</span></code> if the type is an object, <code class=highlight><span class=nb>false</span></code> otherwise.</p> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">¶</a></h2> <p>No-throw guarantee: this function never throws exceptions.</p> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">¶</a></h2> <p>Constant.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">¶</a></h2> <details class=example> <summary>Example</summary> <p>The example below classifies several parsed documents by the type of their root value, without materializing any of them into a <code>BasicJsonType</code> value.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><iostream></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json_view.hpp></span>
|
||||
|
||||
<span class=k>using</span><span class=w> </span><span class=n>json_document</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
|
||||
<span class=kt>int</span><span class=w> </span><span class=nf>main</span><span class=p>()</span>
|
||||
<span class=p>{</span>
|
||||
|
||||
@@ -28,7 +28,7 @@ The example below classifies several parsed documents by the type of their root
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -29,7 +29,7 @@ Constant.
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -1,8 +1,8 @@
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/is_primitive/" rel="canonical"><link href=../is_object/ rel=prev><link href=../is_string/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>is_primitive - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#nlohmannbasic_json_viewis_primitive class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> is_primitive </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 Line truncated
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/is_primitive/" rel="canonical"><link href=../is_object/ rel=prev><link href=../is_string/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>is_primitive - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#nlohmannbasic_json_viewis_primitive class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> is_primitive </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 Line truncated
|
||||
</code></pre></div> <p>This function returns <code class=highlight><span class=nb>true</span></code> if and only if the value is primitive, i.e. <code class=highlight><span class=kc>null</span></code>, a boolean, a number, or a string. It is defined as <code class=highlight><span class=n>is_null</span><span class=p>()</span><span class=w> </span><span class=o>||</span><span class=w> </span><span class=n>is_string</span><span class=p>()</span><span class=w> </span><span class=o>||</span><span class=w> </span><span class=n>is_boolean</span><span class=p>()</span><span class=w> </span><span class=o>||</span><span class=w> </span><span class=n>is_number</span><span class=p>()</span></code>.</p> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">¶</a></h2> <p><code class=highlight><span class=nb>true</span></code> if the type is primitive, <code class=highlight><span class=nb>false</span></code> otherwise.</p> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">¶</a></h2> <p>No-throw guarantee: this function never throws exceptions.</p> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">¶</a></h2> <p>Constant.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">¶</a></h2> <details class=example> <summary>Example</summary> <p>The example below classifies several parsed documents by the type of their root value, without materializing any of them into a <code>BasicJsonType</code> value.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><iostream></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json_view.hpp></span>
|
||||
|
||||
<span class=k>using</span><span class=w> </span><span class=n>json_document</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
|
||||
<span class=kt>int</span><span class=w> </span><span class=nf>main</span><span class=p>()</span>
|
||||
<span class=p>{</span>
|
||||
|
||||
@@ -28,7 +28,7 @@ The example below classifies several parsed documents by the type of their root
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -29,7 +29,7 @@ Constant.
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -1,8 +1,8 @@
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/is_string/" rel="canonical"><link href=../is_primitive/ rel=prev><link href=../is_structured/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>is_string - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> is_string </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark 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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/is_string/" rel="canonical"><link href=../is_primitive/ rel=prev><link href=../is_structured/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>is_string - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> is_string </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark 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4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 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|
||||
</code></pre></div> <p>This function returns <code class=highlight><span class=nb>true</span></code> if and only if the value is a string.</p> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">¶</a></h2> <p><code class=highlight><span class=nb>true</span></code> if the type is a string, <code class=highlight><span class=nb>false</span></code> otherwise.</p> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">¶</a></h2> <p>No-throw guarantee: this function never throws exceptions.</p> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">¶</a></h2> <p>Constant.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">¶</a></h2> <details class=example> <summary>Example</summary> <p>The example below classifies several parsed documents by the type of their root value, without materializing any of them into a <code>BasicJsonType</code> value.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><iostream></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json_view.hpp></span>
|
||||
|
||||
<span class=k>using</span><span class=w> </span><span class=n>json_document</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
|
||||
<span class=kt>int</span><span class=w> </span><span class=nf>main</span><span class=p>()</span>
|
||||
<span class=p>{</span>
|
||||
|
||||
@@ -28,7 +28,7 @@ The example below classifies several parsed documents by the type of their root
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -29,7 +29,7 @@ Constant.
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -1,8 +1,8 @@
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/is_structured/" rel="canonical"><link href=../is_string/ rel=prev><link href=../items/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>is_structured - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> is_structured </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to 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4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 Line truncated
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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/is_structured/" rel="canonical"><link href=../is_string/ rel=prev><link href=../items/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>is_structured - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#nlohmannbasic_json_viewis_structured class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> is_structured </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 Line truncated
|
||||
</code></pre></div> <p>This function returns <code class=highlight><span class=nb>true</span></code> if and only if the value is structured, i.e. an array or an object. It is defined as <code class=highlight><span class=n>is_array</span><span class=p>()</span><span class=w> </span><span class=o>||</span><span class=w> </span><span class=n>is_object</span><span class=p>()</span></code>.</p> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">¶</a></h2> <p><code class=highlight><span class=nb>true</span></code> if the type is structured, <code class=highlight><span class=nb>false</span></code> otherwise.</p> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">¶</a></h2> <p>No-throw guarantee: this function never throws exceptions.</p> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">¶</a></h2> <p>Constant.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">¶</a></h2> <details class=example> <summary>Example</summary> <p>The example below classifies several parsed documents by the type of their root value, without materializing any of them into a <code>BasicJsonType</code> value.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><iostream></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json_view.hpp></span>
|
||||
|
||||
<span class=k>using</span><span class=w> </span><span class=n>json_document</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
|
||||
<span class=kt>int</span><span class=w> </span><span class=nf>main</span><span class=p>()</span>
|
||||
<span class=p>{</span>
|
||||
|
||||
@@ -28,7 +28,7 @@ The example below classifies several parsed documents by the type of their root
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -70,7 +70,7 @@ and [`contains`](contains.md), which resolve to the *first* member with a given
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -1,4 +1,4 @@
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/items/" rel="canonical"><link href=../is_structured/ rel=prev><link href=../materialize/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>items - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#nlohmannbasic_json_viewitems class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> items </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5"/Line truncated
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/items/" rel="canonical"><link href=../is_structured/ rel=prev><link href=../materialize/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>items - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#nlohmannbasic_json_viewitems class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> items </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5"/Line truncated
|
||||
</code></pre></div> <p>Returns a range of items -- (key, value) pairs -- for use in range-based for loops. An item's <code class=highlight><span class=n>key</span><span class=p>()</span></code> is a <code class=highlight><span class=n>string_view_t</span></code> (for an array element, its index converted to a string, as for <a href=../../basic_json/items/ ><code>BasicJsonType::items()</code></a>), and its <code class=highlight><span class=n>value</span><span class=p>()</span></code> is a <code>basic_json_view</code> of the element.</p> <p>The returned type is not part of the public <abbr title="Application Programming Interface">API</abbr> and may change between versions; use a range-based for loop (see the example), or <code class=highlight><span class=k>decltype</span><span class=p>(</span><span class=n>v</span><span class=p>.</span><span class=n>items</span><span class=p>())</span></code> if you need to name it.</p> <div class=highlight><pre><span></span><code><span class=k>for</span><span class=w> </span><span class=p>(</span><span class=k>const</span><span class=w> </span><span class=k>auto</span><span class=o>&</span><span class=w> </span><span class=n>item</span><span class=w> </span><span class=o>:</span><span class=w> </span><span class=n>v</span><span class=p>.</span><span class=n>items</span><span class=p>())</span>
|
||||
<span class=p>{</span>
|
||||
<span class=w> </span><span class=n>std</span><span class=o>::</span><span class=n>cout</span><span class=w> </span><span class=o><<</span><span class=w> </span><span class=s>"key: "</span><span class=w> </span><span class=o><<</span><span class=w> </span><span class=n>item</span><span class=p>.</span><span class=n>key</span><span class=p>()</span><span class=w> </span><span class=o><<</span><span class=w> </span><span class=s>", value: "</span><span class=w> </span><span class=o><<</span><span class=w> </span><span class=n>item</span><span class=p>.</span><span class=n>value</span><span class=p>()</span><span class=w> </span><span class=o><<</span><span class=w> </span><span class=sc>'\n'</span><span class=p>;</span>
|
||||
@@ -10,7 +10,7 @@
|
||||
</code></pre></div> <p>Note the <code class=highlight><span class=k>const</span><span class=w> </span><span class=k>auto</span></code> (by value), not <code class=highlight><span class=k>const</span><span class=w> </span><span class=k>auto</span><span class=o>&</span></code>: unlike <code>BasicJsonType::items()</code>, whose elements are references into an existing object, a view's <code>item</code> is produced on the fly for each step of the iteration, so there is nothing for a reference to bind to.</p> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">¶</a></h2> <p>A range whose iterators dereference to an item (with <code class=highlight><span class=n>key</span><span class=p>()</span></code> and <code class=highlight><span class=n>value</span><span class=p>()</span></code>, see above) and whose <code class=highlight><span class=n>begin</span><span class=p>()</span></code>/<code class=highlight><span class=n>end</span><span class=p>()</span></code> are equivalent to <a href=../begin/ ><code>basic_json_view::begin()</code></a>/<a href=../end/ ><code>end()</code></a>, in document order.</p> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">¶</a></h2> <p>No-throw guarantee: this function never throws exceptions.</p> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">¶</a></h2> <p>Constant.</p> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">¶</a></h2> <p>As for <a href=../begin/ ><code>begin()</code></a>/<a href=../end/ ><code>end()</code></a>, <code>items()</code> visits <strong>every</strong> member of an object, including all occurrences of a duplicate key -- unlike <a href=../operator%5B%5D/ ><code>operator[]</code></a>, <a href=../at/ ><code>at</code></a>, <a href=../find/ ><code>find</code></a>, and <a href=../contains/ ><code>contains</code></a>, which resolve to the <em>first</em> member with a given key. See the <a href=../operator%5B%5D/#notes>Notes on duplicate keys</a> of <code>operator[]</code>.</p> <div class="admonition danger"> <p class=admonition-title>Lifetime issues</p> <p>Unlike <code>BasicJsonType::items()</code> (see <a href="https://github.com/nlohmann/json/issues/2040">#2040</a>), calling <code>items()</code> on a temporary view is safe, for instance <code class=highlight><span class=k>for</span><span class=w> </span><span class=p>(</span><span class=k>auto</span><span class=w> </span><span class=n>item</span><span class=w> </span><span class=o>:</span><span class=w> </span><span class=n>v</span><span class=p>[</span><span class=s>"a"</span><span class=p>].</span><span class=n>items</span><span class=p>())</span></code>: the returned range holds a copy of the view. What must outlive the loop is the document and, for a borrowed document, the source buffer.</p> </div> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">¶</a></h2> <details class=example> <summary>Example</summary> <p>The example below shows a settings object whose source text records every update to a key as a duplicate member, in the order they happened. <code>items()</code> walks all of them, so the update history is visible, while <a href=../operator%5B%5D/ ><code>operator[]</code></a> only ever sees the <em>first</em> one and <a href=../materialize/ ><code>materialize()</code></a> -- like <a href=../../basic_json/parse/ ><code>BasicJsonType::parse()</code></a> -- keeps only the <em>last</em>.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><iostream></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json_view.hpp></span>
|
||||
|
||||
<span class=k>using</span><span class=w> </span><span class=n>json_document</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
|
||||
<span class=kt>int</span><span class=w> </span><span class=nf>main</span><span class=p>()</span>
|
||||
<span class=p>{</span>
|
||||
|
||||
@@ -56,7 +56,7 @@ The example below shows a settings object whose source text records every update
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -53,7 +53,7 @@ never caches the result.
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -1,9 +1,9 @@
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/materialize/" rel="canonical"><link href=../items/ rel=prev><link href=../number_format/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>materialize - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#nlohmannbasic_json_viewmaterialize class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> materialize </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 1Line truncated
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/materialize/" rel="canonical"><link href=../items/ rel=prev><link href=../number_format/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>materialize - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#nlohmannbasic_json_viewmaterialize class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> materialize </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 1Line truncated
|
||||
</code></pre></div> <p>Builds the <code>BasicJsonType</code> value of this subtree: the value <a href=../../basic_json/parse/ ><code>BasicJsonType::parse()</code></a> would have produced for the same source text, allocated for the first time by this call.</p> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">¶</a></h2> <p>The <code>BasicJsonType</code> value of this subtree, or a discarded <code>BasicJsonType</code> value (<code class=highlight><span class=n>BasicJsonType</span><span class=p>(</span><span class=n>value_t</span><span class=o>::</span><span class=n>discarded</span><span class=p>)</span></code>) if the view is <a href=../is_discarded/ >discarded</a>.</p> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">¶</a></h2> <p>Strong guarantee: there are no changes to the view or the document it refers to (nothing about either is mutated by this function).</p> <h2 id=exceptions>Exceptions<a class=headerlink href=#exceptions title="Permanent link">¶</a></h2> <p>May throw <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>bad_alloc</span></code> (via <code>BasicJsonType</code>'s allocator) if constructing the result fails.</p> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">¶</a></h2> <p>Linear in the size of the subtree.</p> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">¶</a></h2> <p><code>materialize()</code> replays the subtree through the same <abbr title="Simple API for XML">SAX</abbr> builder <a href=../../basic_json/parse/ ><code>BasicJsonType::parse()</code></a> uses, so the result matches it exactly -- including, for an object, that a repeated key keeps only its last value. The replay is iterative, so it is not limited by the call stack the way a naive recursive conversion would be; the <abbr title="JavaScript Object Notation">JSON</abbr> nesting depth is limited only by available memory, as for <code>BasicJsonType::parse()</code> itself.</p> <p>Unlike parsing with <a href=../../macros/json_diagnostic_positions/ ><code>JSON_DIAGNOSTIC_POSITIONS</code></a> enabled, the values produced by <code>materialize()</code> do not carry source positions. The index has the start offset of every value, but not the end of arrays, objects, and escaped strings, which the positions also need.</p> <p>Calling <code>materialize()</code> on the same view repeatedly builds a new, independent <code>BasicJsonType</code> value each time; it never caches the result.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">¶</a></h2> <details class=example> <summary>Example</summary> <p>The example below skips messages that are not useful -- a discarded value, or an empty array -- using only <a href=../is_array/ ><code>is_array()</code></a> and <a href=../empty/ ><code>empty()</code></a>, and calls <code>materialize()</code> only for the messages that are actually used, so no <code>BasicJsonType</code> value (and none of its per-element allocations) is ever built for the skipped ones.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><array></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><iostream></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json_view.hpp></span>
|
||||
|
||||
<span class=k>using</span><span class=w> </span><span class=n>json_document</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
|
||||
<span class=kt>int</span><span class=w> </span><span class=nf>main</span><span class=p>()</span>
|
||||
<span class=p>{</span>
|
||||
|
||||
@@ -41,7 +41,7 @@ The example below skips messages that are not useful -- a discarded value, or an
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using nlohmann::json_document;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -33,8 +33,8 @@ source
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using json_view = nlohmann::json_view;
|
||||
using nlohmann::json_document;
|
||||
using nlohmann::json_view;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -1,12 +1,12 @@
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/number_format/" rel="canonical"><link href=../materialize/ rel=prev><link href=../number_token/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>number_format - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#nlohmannbasic_json_viewnumber_format class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> number_format </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to 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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/number_format/" rel="canonical"><link href=../materialize/ rel=prev><link href=../number_token/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>number_format - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> number_format </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to 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4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9Line truncated
|
||||
<span class=w> </span><span class=n>shortest</span><span class=p>,</span>
|
||||
<span class=w> </span><span class=n>source</span>
|
||||
<span class=p>};</span>
|
||||
</code></pre></div> <p>This enumeration is used in <a href=../dump/ ><code>dump</code></a> to choose how numbers are written. Two values are differentiated:</p> <dl> <dt>shortest</dt> <dd>integers are copied from the source text -- already canonical in <abbr title="JavaScript Object Notation">JSON</abbr> -- except that <code class=highlight><span class=mi>-0</span></code> becomes <code class=highlight><span class=mi>0</span></code>, the way <a href=../../basic_json/parse/ ><code>BasicJsonType::parse()</code></a> reads it; floats are written with the library's shortest round-trip conversion, exactly as <a href=../../basic_json/dump/ ><code>BasicJsonType::dump()</code></a> would (e.g. <code class=highlight><span class=mf>1.5</span></code>, <code class=highlight><span class=mf>100.0</span></code>, <code class=highlight><span class=mf>1e+100</span></code>)</dd> <dt>source</dt> <dd>every number is copied exactly as it appears in the source text -- <code class=highlight><span class=mf>1.50</span></code>, <code class=highlight><span class=mf>1E2</span></code>, <code class=highlight><span class=mi>-0</span></code>, all digits of an integer literal with more digits than any number type holds -- something <code>BasicJsonType</code> cannot do, since parsing already reduces every number to its parsed value</dd> </dl> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">¶</a></h2> <details class=example> <summary>Example</summary> <p>The example below writes back a price list received from a supplier: with <code>number_format::shortest</code> (the default), a trailing zero and scientific notation are normalized away and a long account number that overflows every number type is rounded, the same way <code class=highlight><span class=n>materialize</span><span class=p>().</span><span class=n>dump</span><span class=p>()</span></code> (or <code>basic_json::dump()</code>) would; <code>number_format::source</code> keeps every number exactly as it was written in the source text instead.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><iostream></span>
|
||||
<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json_view.hpp></span>
|
||||
|
||||
<span class=k>using</span><span class=w> </span><span class=n>json_document</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>json_view</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_view</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_view</span><span class=p>;</span>
|
||||
|
||||
<span class=kt>int</span><span class=w> </span><span class=nf>main</span><span class=p>()</span>
|
||||
<span class=p>{</span>
|
||||
|
||||
@@ -23,8 +23,8 @@ The example below writes back a price list received from a supplier: with `numbe
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using json_view = nlohmann::json_view;
|
||||
using nlohmann::json_document;
|
||||
using nlohmann::json_view;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -55,8 +55,8 @@ buffer -- and is valid exactly as long as that text is, see the [validity rules]
|
||||
#include <iostream>
|
||||
#include <nlohmann/json_view.hpp>
|
||||
|
||||
using json_document = nlohmann::json_document;
|
||||
using json_view = nlohmann::json_view;
|
||||
using nlohmann::json_document;
|
||||
using nlohmann::json_view;
|
||||
|
||||
int main()
|
||||
{
|
||||
|
||||
@@ -1,9 +1,9 @@
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/number_token/" rel="canonical"><link href=../number_format/ rel=prev><link href=../operator_ltlt/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>number_token - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> number_token </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.Line truncated
|
||||
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/basic_json_view/number_token/" rel="canonical"><link href=../number_format/ rel=prev><link href=../operator_ltlt/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>number_token - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new 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</code></pre></div> <p>Returns the number exactly as it appears in the source text, without parsing or rounding it.</p> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">¶</a></h2> <p>The number's token text, as a <a href=../#member-types><code>string_view_t</code></a> into the document's <a href=../../basic_json_document/source/ ><code>source()</code></a> text -- for example <code class=highlight><span class=s>"1.50"</span></code>, <code class=highlight><span class=s>"1E2"</span></code>, <code class=highlight><span class=s>"-0"</span></code>, or an integer literal with more digits than any number type holds (such as a 30-digit integer, which <a href=../get/ ><code>get<T>()</code></a> and <a href=../materialize/ ><code>materialize()</code></a> can only represent approximately, as a <code>number_float_t</code>).</p> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">¶</a></h2> <p>Strong guarantee: there are no changes to the view or the document it refers to.</p> <h2 id=exceptions>Exceptions<a class=headerlink href=#exceptions title="Permanent link">¶</a></h2> <p>Throws <a href=../../../home/exceptions/#jsonexceptiontype_error302><code>type_error.302</code></a> if the value is not a number; example: <code>"type must be number, but is string"</code>.</p> <p>This exception does not carry a <a href=../../macros/json_diagnostics/ ><code>JSON_DIAGNOSTICS</code></a> path: the view has no <code>BasicJsonType</code> value to point at, so the exception is created without one, even if <code>BasicJsonType</code> was built with <code>JSON_DIAGNOSTICS</code> enabled.</p> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">¶</a></h2> <p>Constant.</p> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">¶</a></h2> <p><code>BasicJsonType</code> has no counterpart to this function: once a number is parsed into <code>number_integer_t</code>, <code>number_unsigned_t</code>, or <code>number_float_t</code>, its original textual form (leading zeros aside, which are already rejected by the grammar; trailing zeros in the fraction; the case and sign of the exponent; ...) is gone. <code>number_token()</code> is useful precisely where that form must survive -- a price or an identifier that must be reproduced exactly, or a number too large for any of <code>BasicJsonType</code>'s number types to hold without loss.</p> <p>The returned <a href=../#member-types><code>string_view_t</code></a> always points into the document's <a href=../../basic_json_document/source/ ><code>source()</code></a> text -- numbers are never decoded into the document's separate string buffer -- and is valid exactly as long as that text is, see the <a href=../ >validity rules</a> of <code>basic_json_view</code>.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">¶</a></h2> <details class=example> <summary>Example</summary> <p>The example below keeps a price and an order ID exactly as they were written in an incoming order, where converting them with <a href=../get/ ><code>get<T>()</code></a> would lose information: the price picks up floating-point rounding, and the order ID -- more digits than a 64-bit integer holds -- can only be approximated as a <code class=highlight><span class=kt>double</span></code> once <code class=highlight><span class=n>materialize</span><span class=p>()</span></code>d.</p> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><iostream></span>
|
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<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json_view.hpp></span>
|
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|
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<span class=k>using</span><span class=w> </span><span class=n>json_document</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
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<span class=k>using</span><span class=w> </span><span class=n>json_view</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_view</span><span class=p>;</span>
|
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<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_document</span><span class=p>;</span>
|
||||
<span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_view</span><span class=p>;</span>
|
||||
|
||||
<span class=kt>int</span><span class=w> </span><span class=nf>main</span><span class=p>()</span>
|
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<span class=p>{</span>
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