deploy: 54f6b3ef06

api/basic_json/operator[]/index.html

@@ -15,7 +15,7 @@
 <span class=c1>// (4)</span>
 <span class=n>reference</span><span class=w> </span><span class=k>operator</span><span class=p>[](</span><span class=k>const</span><span class=w> </span><span class=n>json_pointer</span><span class=o>&amp;</span><span class=w> </span><span class=n>ptr</span><span class=p>);</span>
 <span class=n>const_reference</span><span class=w> </span><span class=k>operator</span><span class=p>[](</span><span class=k>const</span><span class=w> </span><span class=n>json_pointer</span><span class=o>&amp;</span><span class=w> </span><span class=n>ptr</span><span class=p>)</span><span class=w> </span><span class=k>const</span><span class=p>;</span>
-</code></pre></div> <ol> <li>Returns a reference to the array element at specified location <code>idx</code>.</li> <li>Returns a reference to the object element with specified key <code>key</code>. The non-const qualified overload takes the key by value.</li> <li>See 2. This overload is only available if <code>KeyType</code> is comparable with <code class=highlight><span class=k>typename</span><span class=w> </span><span class=nc>object_t</span><span class=o>::</span><span class=n>key_type</span></code> and <code class=highlight><span class=k>typename</span><span class=w> </span><span class=nc>object_comparator_t</span><span class=o>::</span><span class=n>is_transparent</span></code> denotes a type.</li> <li>Returns a reference to the element with specified <abbr title="JavaScript Object Notation">JSON</abbr> pointer <code>ptr</code>.</li> </ol> <h2 id=template-parameters>Template parameters<a class=headerlink href=#template-parameters title="Permanent link">&para;</a></h2> <dl> <dt><code>KeyType</code></dt> <dd>A type for an object key other than <a href=../../json_pointer/ ><code>json_pointer</code></a> that is comparable with <a href=../string_t/ ><code>string_t</code></a> using <a href=../object_comparator_t/ ><code>object_comparator_t</code></a>. This can also be a string view (C++17).</dd> </dl> <h2 id=iterator-invalidation>Iterator invalidation<a class=headerlink href=#iterator-invalidation title="Permanent link">&para;</a></h2> <p>For the non-const versions 1. and 4., when passing an <strong>array</strong> index that does not exist, it is created and filled with a <code class=highlight><span class=kc>null</span></code> value before a reference to it is returned. For this, a reallocation can happen, in which case all iterators (including the <a href=../end/ ><code>end()</code></a> iterator) and all references to the elements are invalidated.</p> <p>For <a href=../../ordered_json/ ><code>ordered_json</code></a>, also passing an <strong>object key</strong> to the non-const versions 2., 3., and 4., a reallocation can happen which again invalidates all iterators and all references.</p> <h2 id=parameters>Parameters<a class=headerlink href=#parameters title="Permanent link">&para;</a></h2> <dl> <dt><code>idx</code> (in)</dt> <dd>index of the element to access</dd> <dt><code>key</code> (in)</dt> <dd>object key of the element to access</dd> <dt><code>ptr</code> (in)</dt> <dd><abbr title="JavaScript Object Notation">JSON</abbr> pointer to the desired element</dd> </dl> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">&para;</a></h2> <ol> <li>(const) reference to the element at index <code>idx</code></li> <li>(const) reference to the element at key <code>key</code></li> <li>(const) reference to the element at key <code>key</code></li> <li>(const) reference to the element pointed to by <code>ptr</code></li> </ol> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">&para;</a></h2> <p>Strong exception safety: if an exception occurs, the original value stays intact.</p> <h2 id=exceptions>Exceptions<a class=headerlink href=#exceptions title="Permanent link">&para;</a></h2> <ol> <li>The function can throw the following exceptions:<ul> <li>Throws <a href=../../../home/exceptions/#jsonexceptiontype_error305><code>type_error.305</code></a> if the <abbr title="JavaScript Object Notation">JSON</abbr> value is not an array or null; in that case, using the <code>[]</code> operator with an index makes no sense.</li> <li>Throws <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>length_error</span></code> if <code>idx</code> equals the maximum value of <code>size_type</code>; the array is left unchanged. (This is the one index for which growing the array to hold it cannot be expressed as a <code>size_type</code> size, the same way an oversized <a href="https://en.cppreference.com/w/cpp/container/vector/resize"><code>resize</code></a> throws.)</li> </ul> </li> <li>The function can throw the following exceptions:<ul> <li>Throws <a href=../../../home/exceptions/#jsonexceptiontype_error305><code>type_error.305</code></a> if the <abbr title="JavaScript Object Notation">JSON</abbr> value is not an object or null; in that case, using the <code>[]</code> operator with a key makes no sense.</li> </ul> </li> <li>See 2.</li> <li> <p>The function can throw the following exceptions:</p> <ul> <li>Throws <a href=../../../home/exceptions/#jsonexceptionparse_error106><code>parse_error.106</code></a> if an array index in the passed <abbr title="JavaScript Object Notation">JSON</abbr> pointer <code>ptr</code> begins with '0'.</li> <li>Throws <a href=../../../home/exceptions/#jsonexceptionparse_error109><code>parse_error.109</code></a> if an array index in the passed <abbr title="JavaScript Object Notation">JSON</abbr> pointer <code>ptr</code> is not a number.</li> <li>Throws <a href=../../../home/exceptions/#jsonexLine truncated
+</code></pre></div> <ol> <li>Returns a reference to the array element at specified location <code>idx</code>.</li> <li>Returns a reference to the object element with specified key <code>key</code>. The non-const qualified overload takes the key by value.</li> <li>See 2. This overload is only available if <code>KeyType</code> is comparable with <code class=highlight><span class=k>typename</span><span class=w> </span><span class=nc>object_t</span><span class=o>::</span><span class=n>key_type</span></code> and <code class=highlight><span class=k>typename</span><span class=w> </span><span class=nc>object_comparator_t</span><span class=o>::</span><span class=n>is_transparent</span></code> denotes a type.</li> <li>Returns a reference to the element with specified <abbr title="JavaScript Object Notation">JSON</abbr> pointer <code>ptr</code>.</li> </ol> <h2 id=template-parameters>Template parameters<a class=headerlink href=#template-parameters title="Permanent link">&para;</a></h2> <dl> <dt><code>KeyType</code></dt> <dd>A type for an object key other than <a href=../../json_pointer/ ><code>json_pointer</code></a> that is comparable with <a href=../string_t/ ><code>string_t</code></a> using <a href=../object_comparator_t/ ><code>object_comparator_t</code></a>. This can also be a string view (C++17).</dd> </dl> <h2 id=iterator-invalidation>Iterator invalidation<a class=headerlink href=#iterator-invalidation title="Permanent link">&para;</a></h2> <p>For the non-const versions 1. and 4., when passing an <strong>array</strong> index that does not exist, it is created and filled with a <code class=highlight><span class=kc>null</span></code> value before a reference to it is returned. For this, a reallocation can happen, in which case all iterators (including the <a href=../end/ ><code>end()</code></a> iterator) and all references to the elements are invalidated.</p> <p>For <a href=../../ordered_json/ ><code>ordered_json</code></a>, also passing an <strong>object key</strong> to the non-const versions 2., 3., and 4., a reallocation can happen which again invalidates all iterators and all references.</p> <h2 id=parameters>Parameters<a class=headerlink href=#parameters title="Permanent link">&para;</a></h2> <dl> <dt><code>idx</code> (in)</dt> <dd>index of the element to access</dd> <dt><code>key</code> (in)</dt> <dd>object key of the element to access</dd> <dt><code>ptr</code> (in)</dt> <dd><abbr title="JavaScript Object Notation">JSON</abbr> pointer to the desired element</dd> </dl> <h2 id=return-value>Return value<a class=headerlink href=#return-value title="Permanent link">&para;</a></h2> <ol> <li>(const) reference to the element at index <code>idx</code></li> <li>(const) reference to the element at key <code>key</code></li> <li>(const) reference to the element at key <code>key</code></li> <li>(const) reference to the element pointed to by <code>ptr</code></li> </ol> <h2 id=exception-safety>Exception safety<a class=headerlink href=#exception-safety title="Permanent link">&para;</a></h2> <p>Strong exception safety: if an exception occurs, the original value stays intact.</p> <h2 id=exceptions>Exceptions<a class=headerlink href=#exceptions title="Permanent link">&para;</a></h2> <ol> <li>The function can throw the following exceptions:<ul> <li>Throws <a href=../../../home/exceptions/#jsonexceptiontype_error305><code>type_error.305</code></a> if the <abbr title="JavaScript Object Notation">JSON</abbr> value is not an array or null; in that case, using the <code>[]</code> operator with an index makes no sense.</li> <li>Throws <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>length_error</span></code> if <code>idx</code> equals the maximum value of <code>size_type</code>; the array is left unchanged. (This is the one index for which growing the array to hold it cannot be expressed as a <code>size_type</code> size, the same way an oversized <a href="https://en.cppreference.com/w/cpp/container/vector/resize"><code>resize</code></a> throws.)</li> </ul> </li> <li>The function can throw the following exceptions:<ul> <li>Throws <a href=../../../home/exceptions/#jsonexceptiontype_error305><code>type_error.305</code></a> if the <abbr title="JavaScript Object Notation">JSON</abbr> value is not an object or null; in that case, using the <code>[]</code> operator with a key makes no sense.</li> </ul> </li> <li>See 2.</li> <li> <p>The function can throw the following exceptions:</p> <ul> <li>Throws <a href=../../../home/exceptions/#jsonexceptionparse_error106><code>parse_error.106</code></a> if an array index in the passed <abbr title="JavaScript Object Notation">JSON</abbr> pointer <code>ptr</code> begins with '0'.</li> <li>Throws <a href=../../../home/exceptions/#jsonexceptionparse_error109><code>parse_error.109</code></a> if an array index in the passed <abbr title="JavaScript Object Notation">JSON</abbr> pointer <code>ptr</code> is not a number.</li> <li>Throws <a href=../../../home/exceptions/#jsonexLine truncated
 <span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
 
 <span class=k>using</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json</span><span class=p>;</span>
@@ -283,4 +283,4 @@
 <span class=s2>"foo"</span>
 <span class=p>[</span><span class=mi>1</span><span class=p>,</span><span class=mi>2</span><span class=p>]</span>
 <span class=mi>2</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=../../../features/element_access/unchecked_access/ >Unchecked access</a> - element access without range checking</li> <li><a href=../../../features/assertions/ >Runtime assertions</a> - assertions guarding against undefined behavior</li> <li><a href=../at/ ><code>at</code></a> - access by reference with range checking</li> <li><a href=../value/ ><code>value</code></a> - access with default value</li> <li><a href=../../basic_json_view/operator%5B%5D/ ><code>basic_json_view::operator[]</code></a> - the same access on a zero-copy view (a duplicate key resolves to the first member, whereas <code>parse()</code> keeps the last; a missing key gives a discarded view instead of undefined behavior)</li> <li><a href=../../../features/element_access/ >Element Access</a> - overview of all ways to access elements</li> <li><a href=../../../features/json_pointer/ ><abbr title="JavaScript Object Notation">JSON</abbr> Pointer</a> - access nested values with a pointer</li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ol> <li>Added in version 1.0.0. Fixed 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> to throw <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>length_error</span></code> instead of emptying the array and accessing it out of bounds when <code>idx</code> equals the maximum value of <code>size_type</code>. A missing index in the const version is guarded by a runtime assertion since 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> <li>Added in version 1.0.0. Added overloads for <code>T* key</code> in version 1.1.0. The <code>T* key</code> overloads forward to overload 3 since version 3.11.0.</li> <li>Added in version 3.11.0. Support for keys convertible to <code>std::string_view</code> 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>, consistently across the lookup functions.</li> <li>Added in version 2.0.0. A missing array index in the const version is guarded by a runtime assertion since version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>. Throws <a href=../../../home/exceptions/#jsonexceptionparse_error109><code>parse_error.109</code></a> instead of <a href=../../../home/exceptions/#jsonexceptionout_of_range404><code>out_of_range.404</code></a> for a one-character array index that is not a digit (e.g., <code>/x</code>) 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>, as it already did for longer ones.</li> </ol> <!-- 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 06:41:42 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> <nav class="md-footer__inner md-grid" aria-label=Footer> <a href=../operator_value_t/ class="md-footer__link md-footer__link--prev" aria-label="Previous: operator value_t"> <div class="md-footer__button md-icon"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M20 11v2H8l5.5 5.5-1.42 1.42L4.16 12l7.92-7.92L13.5 5.5 8 11z"/></svg> </div> <div class=md-footer__title> <span class=md-footer__dLine truncated
+</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=../../../features/element_access/unchecked_access/ >Unchecked access</a> - element access without range checking</li> <li><a href=../../../features/assertions/ >Runtime assertions</a> - assertions guarding against undefined behavior</li> <li><a href=../at/ ><code>at</code></a> - access by reference with range checking</li> <li><a href=../value/ ><code>value</code></a> - access with default value</li> <li><a href=../../basic_json_view/operator%5B%5D/ ><code>basic_json_view::operator[]</code></a> - the same access on a zero-copy view (a duplicate key resolves to the first member, whereas <code>parse()</code> keeps the last; a missing key gives a discarded view instead of undefined behavior)</li> <li><a href=../../../features/element_access/ >Element Access</a> - overview of all ways to access elements</li> <li><a href=../../../features/json_pointer/ ><abbr title="JavaScript Object Notation">JSON</abbr> Pointer</a> - access nested values with a pointer</li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ol> <li>Added in version 1.0.0. Fixed 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> to throw <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>length_error</span></code> instead of emptying the array and accessing it out of bounds when <code>idx</code> equals the maximum value of <code>size_type</code>. A missing index in the const version is guarded by a runtime assertion since 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> <li>Added in version 1.0.0. Added overloads for <code>T* key</code> in version 1.1.0. The <code>T* key</code> overloads forward to overload 3 since version 3.11.0.</li> <li>Added in version 3.11.0. Support for keys convertible to <code>std::string_view</code> 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>, consistently across the lookup functions.</li> <li>Added in version 2.0.0. A missing array index in the const version is guarded by a runtime assertion since version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>. Throws <a href=../../../home/exceptions/#jsonexceptionparse_error109><code>parse_error.109</code></a> instead of <a href=../../../home/exceptions/#jsonexceptionout_of_range404><code>out_of_range.404</code></a> for a one-character array index that is not a digit (e.g., <code>/x</code>) 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>, as it already did for longer ones. Fixed 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> to leave the value unchanged if the non-const version throws (strong exception safety, as documented); before, values created for earlier reference tokens of <code>ptr</code> were kept.</li> </ol> <!-- 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 16:15:55 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> <nav class="md-footer__inner md-grid" aria-label=Footer> <a href=../operator_value_t/ cLine truncated