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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_document/insert/" rel="canonical"><link href=../erase/ 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>insert - 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 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<span class=n>view_type</span><span class=w> </span><span class=n>insert</span><span class=p>(</span><span class=n>view_type</span><span class=w> </span><span class=n>array</span><span class=p>,</span><span class=w> </span><span class=n>I</span><span class=w> </span><span class=n>idx</span><span class=p>,</span><span class=w> </span><span class=n>V</span><span class=o>&amp;&amp;</span><span class=w> </span><span class=n>value</span><span class=p>);</span>
</code></pre></div> <p>Only 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>, e.g. <a href=../../json_editable_document/ ><code>json_editable_document</code></a>) has <code>insert</code>; calling it on a read-only <code>basic_json_document</code> fails to compile (<code class=highlight><span class=k>static_assert</span></code>).</p> <p>Inserts <code>value</code> into <code>array</code> as a new element before position <code>idx</code>, which must not be past the end (<code class=highlight><span class=n>idx</span><span class=w> </span><span class=o>&lt;=</span><span class=w> </span><span class=n>array</span><span class=p>.</span><span class=n>size</span><span class=p>()</span></code>; <code class=highlight><span class=n>idx</span><span class=w> </span><span class=o>==</span><span class=w> </span><span class=n>array</span><span class=p>.</span><span class=n>size</span><span class=p>()</span></code> appends, like <a href=../push_back/ ><code>push_back</code></a>). Unlike <a href=../push_back/ ><code>push_back</code></a>, a <a href=../../basic_json_view/is_null/ >null</a> <code>array</code> does <em>not</em> first become an empty array: <code>array</code> must already be an array.</p> <p><code>value</code> is accepted three ways: a <a href=../../basic_json_view/ ><code>basic_json_view</code></a> of <em>any</em> document -- read-only or editable, and it does not have to be <code>array</code>'s own document -- which is copied so that nothing is shared with the source document afterward; a <code>BasicJsonType</code> value; or anything <code>BasicJsonType</code> can be constructed from (numbers, strings, <code class=highlight><span class=kt>bool</span></code>, <code class=highlight><span class=nb>nullptr</span></code>, containers, ...).</p> <h2 id=template-parameters>Template parameters<a class=headerlink href=#template-parameters title="Permanent link">&para;</a></h2> <dl> <dt><code>I</code></dt> <dd>an integral type other than <code class=highlight><span class=kt>bool</span></code>, deduced (overloads taking a <code class=highlight><span class=kt>bool</span></code> or a non-integral type for <code>idx</code> do not participate in overload resolution).</dd> <dt><code>V</code></dt> <dd>the type of <code>value</code>, deduced; see above for what is accepted.</dd> </dl> <h2 id=parameters>Parameters<a class=headerlink href=#parameters title="Permanent link">&para;</a></h2> <dl> <dt><code>array</code> (in)</dt> <dd>the array to insert into</dd> <dt><code>idx</code> (in)</dt> <dd>the position to insert <code>value</code> before; a negative value throws (see <a href=#exceptions>Exceptions</a>)</dd> <dt><code>value</code> (in)</dt> <dd>the value to insert</dd> </dl> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">&para;</a></h2> <p>a view of the new element, now holding <code>value</code></p> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">&para;</a></h2> <p>Basic exception safety: <code>value</code> is fully encoded -- including the checks below -- into storage owned by the document before anything already reachable from <a href=../root/ ><code>root()</code></a> is touched, so a failure while encoding <code>value</code> (an invalid argument, or <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>bad_alloc</span></code>) leaves the document completely unchanged, other than memory allocated for the encoding that is not reclaimed. A failure of a later allocation -- while <code>array</code> switches from its parsed layout to a growable block, or while that block grows, see <a href=#notes>Notes</a> -- can still leave <code>array</code> already switched to that layout even though <code>value</code> itself was not inserted.</p> <h2 id=exceptions>Exceptions<a class=headerlink href=#exceptions title="Permanent link">&para;</a></h2> <p>Throws <a href=../../../home/exceptions/#jsonexceptiontype_error309><code>type_error.309</code></a> if <code>array</code> is not an array -- the same message <a href=../../basic_json/insert/ ><code>BasicJsonType::insert</code></a> throws for the same type; a null <code>array</code> throws this too (see above). Throws <a href=../../../home/exceptions/#jsonexceptionout_of_range401><code>out_of_range.401</code></a> if <code>idx</code> is negative, or if <code class=highlight><span class=n>idx</span><span class=w> </span><span class=o>&gt;</span><span class=w> </span><span class=n>array</span><span class=p>.</span><span class=n>size</span><span class=p>()</span></code>. Throws <a href=../../../home/exceptions/#jsonexceptioninvalid_iterator202><code>invalid_iterator.202</code></a> ("view does not belong to this document") if <code>array</code> is a <a href=../../basic_json_view/is_discarded/ >discarded</a> view or a view of a <em>dLine truncated
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json_view.hpp&gt;</span>