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@@ -23,6 +23,10 @@ Linear in [`node_count()`](node_count.md) plus the length of the decoded strings
## Notes
The node index of a small document (an estimate of up to 1024 nodes, which is up to about 4 KiB of minified text) is
allocated together with the document's header, so that parsing needs one allocation. That part cannot be released
separately: `shrink_to_fit()` only trims a node index that has its own allocation, and the decoded strings.
!!! warning "Invalidates views"
Unlike moving the document, `shrink_to_fit()` **invalidates every view taken from this document before the
@@ -1,5 +1,5 @@
<!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/shrink_to_fit/" rel="canonical"><link href=../set/ rel=prev><link href=../source/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>shrink_to_fit - 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>Releases capacity that is no longer needed, both of the node index and of the buffer for decoded strings (strings that contained escape sequences), e.g. after <a href=../read/ ><code>read()</code></a> replaced a large document with a much smaller one. Like <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>vector</span><span class=o>::</span><span class=n>shrink_to_fit</span><span class=p>()</span></code>, this is a non-binding request: the library may keep more capacity than strictly necessary.</p> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">&para;</a></h2> <p>Strong guarantee: if an exception is thrown, there are no changes to the document.</p> <h2 id=exceptions>Exceptions<a class=headerlink href=#exceptions title="Permanent link">&para;</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 the reallocation fails; on exception, the document is unchanged.</p> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">&para;</a></h2> <p>Linear in <a href=../node_count/ ><code>node_count()</code></a> plus the length of the decoded strings.</p> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">&para;</a></h2> <div class="admonition warning"> <p class=admonition-title>Invalidates views</p> <p>Unlike moving the document, <code>shrink_to_fit()</code> <strong>invalidates every view taken from this document before the call</strong>, including a previously obtained <a href=../root/ ><code>root()</code></a>: the node index is moved into a new, smaller allocation, and the old one is freed. Take a fresh view from <a href=../root/ ><code>root()</code></a> after calling this function.</p> </div> <p>This is unlike <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>vector</span><span class=o>::</span><span class=n>shrink_to_fit</span><span class=p>()</span></code>, which promises nothing about validity but in practice often leaves iterators alone when it did not need to reallocate; here, an implementation that avoids a reallocation when possible would be an internal optimization only, not a guarantee to rely on.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example</summary> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;iostream&gt;</span>
</code></pre></div> <p>Releases capacity that is no longer needed, both of the node index and of the buffer for decoded strings (strings that contained escape sequences), e.g. after <a href=../read/ ><code>read()</code></a> replaced a large document with a much smaller one. Like <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>vector</span><span class=o>::</span><span class=n>shrink_to_fit</span><span class=p>()</span></code>, this is a non-binding request: the library may keep more capacity than strictly necessary.</p> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">&para;</a></h2> <p>Strong guarantee: if an exception is thrown, there are no changes to the document.</p> <h2 id=exceptions>Exceptions<a class=headerlink href=#exceptions title="Permanent link">&para;</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 the reallocation fails; on exception, the document is unchanged.</p> <h2 id=complexity>Complexity<a class=headerlink href=#complexity title="Permanent link">&para;</a></h2> <p>Linear in <a href=../node_count/ ><code>node_count()</code></a> plus the length of the decoded strings.</p> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">&para;</a></h2> <p>The node index of a small document (an estimate of up to 1024 nodes, which is up to about 4 KiB of minified text) is allocated together with the document's header, so that parsing needs one allocation. That part cannot be released separately: <code>shrink_to_fit()</code> only trims a node index that has its own allocation, and the decoded strings.</p> <div class="admonition warning"> <p class=admonition-title>Invalidates views</p> <p>Unlike moving the document, <code>shrink_to_fit()</code> <strong>invalidates every view taken from this document before the call</strong>, including a previously obtained <a href=../root/ ><code>root()</code></a>: the node index is moved into a new, smaller allocation, and the old one is freed. Take a fresh view from <a href=../root/ ><code>root()</code></a> after calling this function.</p> </div> <p>This is unlike <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>vector</span><span class=o>::</span><span class=n>shrink_to_fit</span><span class=p>()</span></code>, which promises nothing about validity but in practice often leaves iterators alone when it did not need to reallocate; here, an implementation that avoids a reallocation when possible would be an internal optimization only, not a guarantee to rely on.</p> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example</summary> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;iostream&gt;</span>
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;sstream&gt;</span>
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;string&gt;</span>
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json_view.hpp&gt;</span>
@@ -46,4 +46,4 @@
</code></pre></div> <p>Output:</p> <div class=highlight><pre><span></span><code><span class=kc>true</span>
<span class=kc>true</span>
<span class=kc>true</span><span class=w> </span><span class=mi>1</span>
</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../node_count/ >node_count</a> - the number of index entries</li> <li><a href=../memory_usage/ >memory_usage</a> - the number of bytes held by the document</li> <li><a href=../root/ >root</a> - the view of the root value</li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</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 &copy; 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</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../node_count/ >node_count</a> - the number of index entries</li> <li><a href=../memory_usage/ >memory_usage</a> - the number of bytes held by the document</li> <li><a href=../root/ >root</a> - the view of the root value</li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</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 27, 2026 06:22:49 UTC">October 27, 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 &copy; 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="noopeneLine truncated
@@ -20,6 +20,8 @@ Linear in [`node_count()`](https://json.nlohmann.me/api/basic_json_document/node
## Notes
The node index of a small document (an estimate of up to 1024 nodes, which is up to about 4 KiB of minified text) is allocated together with the document's header, so that parsing needs one allocation. That part cannot be released separately: `shrink_to_fit()` only trims a node index that has its own allocation, and the decoded strings.
Invalidates views
Unlike moving the document, `shrink_to_fit()` **invalidates every view taken from this document before the call**, including a previously obtained [`root()`](https://json.nlohmann.me/api/basic_json_document/root/index.md): the node index is moved into a new, smaller allocation, and the old one is freed. Take a fresh view from [`root()`](https://json.nlohmann.me/api/basic_json_document/root/index.md) after calling this function.
+1 -1
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@@ -1 +1 @@
{"config":{"lang":["en"],"separator":"[\\s\\-\\.]","pipeline":["stopWordFilter"],"fields":{"title":{"boost":1000.0},"text":{"boost":1.0},"tags":{"boost":1000000.0}}},"docs":[{"location":"","title":"JSON for Modern C++","text":"<p>JSON for Modern C++ is a header-only C++11 library that turns JSON into a first-class C++ data type, using the operator magic of modern C++ so that creating, reading, and modifying JSON values feels as natural as it does in languages like Python. The whole library is available as a single header, <code>json.hpp</code>, with no dependencies, no subproject, and no complex build system to set up; a companion header, <code>json_fwd.hpp</code>, provides forward declarations to keep compile times down, <code>&lt;nlohmann/json_literals.hpp&gt;</code> holds the user-defined string literals on their own, and <code>&lt;nlohmann/json_view.hpp&gt;</code> adds zero-copy views and editable documents. See header-only integration for details. It is heavily unit-tested with 100% code coverage, checked with Valgrind and the Clang Sanitizers for memory leaks, and continuously fuzz-tested by Google OSS-Fuzz.</p>"},{"location":"#quick-start","title":"Quick start","text":"<p>Add the single header to your project and use the library like this:</p> <pre><code>#include &lt;iostream&gt;\n#include &lt;nlohmann/json.hpp&gt;\n\nusing nlohmann::json;\n\nint main()\n{\n // parse a JSON string\n json j = json::parse(R\"({\"happy\": true, \"pi\": 3.141})\");\n\n // access and modify values\n j[\"name\"] = \"Niels\";\n j[\"list\"] = {1, 0, 2};\n\n // read a value into a C++ variable and use it\n double pi = j[\"pi\"].get&lt;double&gt;();\n std::cout &lt;&lt; \"2 * pi = \" &lt;&lt; 2 * pi &lt;&lt; '\\n';\n\n // serialize with an indent of 4 spaces\n std::cout &lt;&lt; j.dump(4) &lt;&lt; '\\n';\n}\n</code></pre> <p>Get the library by copying the single header <code>json.hpp</code> from the releases page into a directory <code>nlohmann</code> on your include path, or by installing it with a package manager:</p> <pre><code>brew install nlohmann-json # Homebrew\nvcpkg install nlohmann-json # vcpkg\n</code></pre> <pre><code>find_package(nlohmann_json 3.12.0 REQUIRED)\ntarget_link_libraries(myproject PRIVATE nlohmann_json::nlohmann_json)\n</code></pre> <p>See Integration for CMake in detail, all supported package managers (Conan, Meson, Bazel, Conda, and more), and pkg-config.</p>"},{"location":"#explore-the-documentation","title":"Explore the documentation","text":"<ul> <li> <p> Features</p> <p>Creating, parsing, accessing, and serializing JSON values, JSON Pointer/Patch, binary formats, zero-copy views, and more.</p> <p> Features</p> </li> <li> <p> Integration</p> <p>Add the library to your project via a single header, CMake, a package manager, or pkg-config.</p> <p> Integration</p> </li> <li> <p> API documentation</p> <p>The complete reference for <code>basic_json</code> and its member functions, types, and related classes, as well as for <code>json_document</code> and <code>json_view</code>.</p> <p> API documentation</p> </li> <li> <p> FAQ</p> <p>Answers to common questions and known surprises when using the library.</p> <p> FAQ</p> </li> <li> <p> Releases</p> <p>What changed in each release, with links to the relevant documentation.</p> <p> Releases</p> </li> <li> <p> Community</p> <p>The ecosystem, contribution guidelines, governance, and quality assurance around the project.</p> <p> Community</p> </li> </ul> <p>Unreleased changes</p> <p>This documentation is built from the <code>develop</code> branch and may describe changes that are not part of a release yet. Their version numbers are followed by an unreleased badge; see Releases for what shipped in each version.</p> <p>The library is licensed under the MIT License. The source code, issue tracker, and discussions are on GitHub.</p>"},{"location":"api/is_json_view/","title":"nlohmann::is_json_view","text":"<p>Defined in header <code>&lt;nlohmann/json_view.hpp&gt;</code></p> <pre><code>template&lt;typename T&gt;\nstruct is_json_view;\n</code></pre> <p>A type trait: <code>is_json_view&lt;T&gt;::value</code> is <code>true</code> if <code>T</code> is a <code>basic_json_view</code> of any <code>BasicJsonType</code> and any <code>view_mode</code> -- <code>json_view</code>, <code>json_editable_view</code>, <code>ordered_json_view</code>, ... -- and <code>false</code> otherwise, for <code>basic_json</code> as well.</p> <p>It is meant for constraining templates that accept views, in particular a <code>from_json()</code> that should read views directly: <code>get&lt;T&gt;()</code> on a view calls a <code>from_json()</code> with the view only if that <code>from_json()</code> accepts views but not arbitrary types.</p>"},{"location":"api/is_json_view/#template-parameters","title":"Template parameters","text":"<code>T</code> the type to check (without cv-qualifiers or references)"},{"location":"api/is_json_view/#notes","title":"Notes","text":"Line truncated
{"config":{"lang":["en"],"separator":"[\\s\\-\\.]","pipeline":["stopWordFilter"],"fields":{"title":{"boost":1000.0},"text":{"boost":1.0},"tags":{"boost":1000000.0}}},"docs":[{"location":"","title":"JSON for Modern C++","text":"<p>JSON for Modern C++ is a header-only C++11 library that turns JSON into a first-class C++ data type, using the operator magic of modern C++ so that creating, reading, and modifying JSON values feels as natural as it does in languages like Python. The whole library is available as a single header, <code>json.hpp</code>, with no dependencies, no subproject, and no complex build system to set up; a companion header, <code>json_fwd.hpp</code>, provides forward declarations to keep compile times down, <code>&lt;nlohmann/json_literals.hpp&gt;</code> holds the user-defined string literals on their own, and <code>&lt;nlohmann/json_view.hpp&gt;</code> adds zero-copy views and editable documents. See header-only integration for details. It is heavily unit-tested with 100% code coverage, checked with Valgrind and the Clang Sanitizers for memory leaks, and continuously fuzz-tested by Google OSS-Fuzz.</p>"},{"location":"#quick-start","title":"Quick start","text":"<p>Add the single header to your project and use the library like this:</p> <pre><code>#include &lt;iostream&gt;\n#include &lt;nlohmann/json.hpp&gt;\n\nusing nlohmann::json;\n\nint main()\n{\n // parse a JSON string\n json j = json::parse(R\"({\"happy\": true, \"pi\": 3.141})\");\n\n // access and modify values\n j[\"name\"] = \"Niels\";\n j[\"list\"] = {1, 0, 2};\n\n // read a value into a C++ variable and use it\n double pi = j[\"pi\"].get&lt;double&gt;();\n std::cout &lt;&lt; \"2 * pi = \" &lt;&lt; 2 * pi &lt;&lt; '\\n';\n\n // serialize with an indent of 4 spaces\n std::cout &lt;&lt; j.dump(4) &lt;&lt; '\\n';\n}\n</code></pre> <p>Get the library by copying the single header <code>json.hpp</code> from the releases page into a directory <code>nlohmann</code> on your include path, or by installing it with a package manager:</p> <pre><code>brew install nlohmann-json # Homebrew\nvcpkg install nlohmann-json # vcpkg\n</code></pre> <pre><code>find_package(nlohmann_json 3.12.0 REQUIRED)\ntarget_link_libraries(myproject PRIVATE nlohmann_json::nlohmann_json)\n</code></pre> <p>See Integration for CMake in detail, all supported package managers (Conan, Meson, Bazel, Conda, and more), and pkg-config.</p>"},{"location":"#explore-the-documentation","title":"Explore the documentation","text":"<ul> <li> <p> Features</p> <p>Creating, parsing, accessing, and serializing JSON values, JSON Pointer/Patch, binary formats, zero-copy views, and more.</p> <p> Features</p> </li> <li> <p> Integration</p> <p>Add the library to your project via a single header, CMake, a package manager, or pkg-config.</p> <p> Integration</p> </li> <li> <p> API documentation</p> <p>The complete reference for <code>basic_json</code> and its member functions, types, and related classes, as well as for <code>json_document</code> and <code>json_view</code>.</p> <p> API documentation</p> </li> <li> <p> FAQ</p> <p>Answers to common questions and known surprises when using the library.</p> <p> FAQ</p> </li> <li> <p> Releases</p> <p>What changed in each release, with links to the relevant documentation.</p> <p> Releases</p> </li> <li> <p> Community</p> <p>The ecosystem, contribution guidelines, governance, and quality assurance around the project.</p> <p> Community</p> </li> </ul> <p>Unreleased changes</p> <p>This documentation is built from the <code>develop</code> branch and may describe changes that are not part of a release yet. Their version numbers are followed by an unreleased badge; see Releases for what shipped in each version.</p> <p>The library is licensed under the MIT License. The source code, issue tracker, and discussions are on GitHub.</p>"},{"location":"api/is_json_view/","title":"nlohmann::is_json_view","text":"<p>Defined in header <code>&lt;nlohmann/json_view.hpp&gt;</code></p> <pre><code>template&lt;typename T&gt;\nstruct is_json_view;\n</code></pre> <p>A type trait: <code>is_json_view&lt;T&gt;::value</code> is <code>true</code> if <code>T</code> is a <code>basic_json_view</code> of any <code>BasicJsonType</code> and any <code>view_mode</code> -- <code>json_view</code>, <code>json_editable_view</code>, <code>ordered_json_view</code>, ... -- and <code>false</code> otherwise, for <code>basic_json</code> as well.</p> <p>It is meant for constraining templates that accept views, in particular a <code>from_json()</code> that should read views directly: <code>get&lt;T&gt;()</code> on a view calls a <code>from_json()</code> with the view only if that <code>from_json()</code> accepts views but not arbitrary types.</p>"},{"location":"api/is_json_view/#template-parameters","title":"Template parameters","text":"<code>T</code> the type to check (without cv-qualifiers or references)"},{"location":"api/is_json_view/#notes","title":"Notes","text":"Line truncated
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