External/json
8
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity
1bda49b536
json/features/json_pointer/index.html

48 lines
64 KiB
HTML
Raw Normal View History

Deployed fe4b663 with MkDocs version: 1.4.2
2023-03-08 15:43:29 +03:00
<!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/features/json_pointer/ rel=canonical><link rel=icon href=../../assets/images/favicon.png><meta name=generator content="mkdocs-1.4.2, mkdocs-material-8.5.10"><title>JSON Pointer - JSON for Modern C++</title><link rel=stylesheet href=../../assets/stylesheets/main.975780f9.min.css><link rel=stylesheet href=../../assets/stylesheets/palette.2505c338.min.css><link rel=preconnect href=https://fonts.gstatic.com crossorigin><link rel=stylesheet href="https://fonts.googleapis.com/css?family=Roboto:300,300i,400,400i,700,700i%7CJetBrains+Mono:400,400i,700,700i&display=fallback"><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> <script>var palette=__md_get("__palette");if(palette&&"object"==typeof palette.color)for(var key of Object.keys(palette.color))document.body.setAttribute("data-md-color-"+key,palette.color[key])</script> <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=#json-pointer 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 3.54Z"/></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 6h18v2H3V6m0 5h18v2H3v-2m0 5h18v2H3v-2Z"/></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> JSON Pointer </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_1> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_2 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 12 20 8.69Z"/></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_2> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_1 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 12c0-2.42-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V
<span class=w> </span><span class=nt>&quot;array&quot;</span><span class=p>:</span><span class=w> </span><span class=p>[</span><span class=s2>&quot;A&quot;</span><span class=p>,</span><span class=w> </span><span class=s2>&quot;B&quot;</span><span class=p>,</span><span class=w> </span><span class=s2>&quot;C&quot;</span><span class=p>],</span><span class=w></span>
<span class=w> </span><span class=nt>&quot;nested&quot;</span><span class=p>:</span><span class=w> </span><span class=p>{</span><span class=w></span>
<span class=w> </span><span class=nt>&quot;one&quot;</span><span class=p>:</span><span class=w> </span><span class=mi>1</span><span class=p>,</span><span class=w></span>
<span class=w> </span><span class=nt>&quot;two&quot;</span><span class=p>:</span><span class=w> </span><span class=mi>2</span><span class=p>,</span><span class=w></span>
<span class=w> </span><span class=nt>&quot;three&quot;</span><span class=p>:</span><span class=w> </span><span class=p>[</span><span class=kc>true</span><span class=p>,</span><span class=w> </span><span class=kc>false</span><span class=p>]</span><span class=w></span>
<span class=w> </span><span class=p>}</span><span class=w></span>
<span class=p>}</span><span class=w></span>
</code></pre></div> <p>Then every value inside the JSON document can be identified as follows:</p> <table> <thead> <tr> <th>JSON Pointer</th> <th>JSON value</th> </tr> </thead> <tbody> <tr> <td>``</td> <td><code class=highlight><span class=p>{</span><span class=nt>&quot;array&quot;</span><span class=p>:[</span><span class=s2>&quot;A&quot;</span><span class=p>,</span><span class=s2>&quot;B&quot;</span><span class=p>,</span><span class=s2>&quot;C&quot;</span><span class=p>],</span><span class=nt>&quot;nested&quot;</span><span class=p>:{</span><span class=nt>&quot;one&quot;</span><span class=p>:</span><span class=mi>1</span><span class=p>,</span><span class=nt>&quot;two&quot;</span><span class=p>:</span><span class=mi>2</span><span class=p>,</span><span class=nt>&quot;three&quot;</span><span class=p>:[</span><span class=kc>true</span><span class=p>,</span><span class=kc>false</span><span class=p>]}}</span><span class=w></span></code></td> </tr> <tr> <td><code>/array</code></td> <td><code class=highlight><span class=p>[</span><span class=s2>&quot;A&quot;</span><span class=p>,</span><span class=s2>&quot;B&quot;</span><span class=p>,</span><span class=s2>&quot;C&quot;</span><span class=p>]</span><span class=w></span></code></td> </tr> <tr> <td><code>/array/0</code></td> <td><code class=highlight><span class=err>A</span><span class=w></span></code></td> </tr> <tr> <td><code>/array/1</code></td> <td><code class=highlight><span class=err>B</span><span class=w></span></code></td> </tr> <tr> <td><code>/array/2</code></td> <td><code class=highlight><span class=err>C</span><span class=w></span></code></td> </tr> <tr> <td><code>/nested</code></td> <td><code class=highlight><span class=p>{</span><span class=nt>&quot;one&quot;</span><span class=p>:</span><span class=mi>1</span><span class=p>,</span><span class=nt>&quot;two&quot;</span><span class=p>:</span><span class=mi>2</span><span class=p>,</span><span class=nt>&quot;three&quot;</span><span class=p>:[</span><span class=kc>true</span><span class=p>,</span><span class=kc>false</span><span class=p>]}</span><span class=w></span></code></td> </tr> <tr> <td><code>/nested/one</code></td> <td><code class=highlight><span class=mi>1</span><span class=w></span></code></td> </tr> <tr> <td><code>/nested/two</code></td> <td><code class=highlight><span class=mi>2</span><span class=w></span></code></td> </tr> <tr> <td><code>/nested/three</code></td> <td><code class=highlight><span class=p>[</span><span class=kc>true</span><span class=p>,</span><span class=kc>false</span><span class=p>]</span><span class=w></span></code></td> </tr> <tr> <td><code>/nested/three/0</code></td> <td><code class=highlight><span class=kc>true</span><span class=w></span></code></td> </tr> <tr> <td><code>/nested/three/1</code></td> <td><code class=highlight><span class=kc>false</span><span class=w></span></code></td> </tr> </tbody> </table> <p>Note <code>/</code> does not identify the root (i.e., the whole document), but an object entry with empty key <code>""</code>. See <a href=https://tools.ietf.org/html/rfc6901>RFC 6901</a> for more information.</p> <h2 id=json-pointer-creation>JSON Pointer creation<a class=headerlink href=#json-pointer-creation title="Permanent link">&para;</a></h2> <p>JSON Pointers can be created from a string:</p> <div class=highlight><pre><span></span><code><span class=n>json</span><span class=o>::</span><span class=n>json_pointer</span><span class=w> </span><span class=n>p</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=s>&quot;/nested/one&quot;</span><span class=p>;</span><span class=w></span>
</code></pre></div> <p>Furthermore, a user-defined string literal can be used to achieve the same result:</p> <div class=highlight><pre><span></span><code><span class=k>auto</span><span class=w> </span><span class=n>p</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=s>&quot;/nested/one&quot;</span><span class=n>_json_pointer</span><span class=p>;</span><span class=w></span>
</code></pre></div> <p>The escaping rules of <a href=https://tools.ietf.org/html/rfc6901>RFC 6901</a> are implemented. See the <a href=../../api/json_pointer/json_pointer/ >constructor documentation</a> for more information.</p> <h2 id=value-access>Value access<a class=headerlink href=#value-access title="Permanent link">&para;</a></h2> <p>JSON Pointers can be used in the <a href=../../api/basic_json/at/ ><code>at</code></a>, <a href=../../api/basic_json/operator%5B%5D/ ><code>operator[]</code></a>, and <a href=../../api/basic_json/value/ ><code>value</code></a> functions just like object keys or array indices.</p> <div class=highlight><pre><span></span><code><span class=c1>// the JSON value from above</span>
<span class=k>auto</span><span class=w> </span><span class=n>j</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>json</span><span class=o>::</span><span class=n>parse</span><span class=p>(</span><span class=sa>R</span><span class=s>&quot;</span><span class=dl>(</span><span class=s>{</span>
<span class=s> &quot;array&quot;: [&quot;A&quot;, &quot;B&quot;, &quot;C&quot;],</span>
<span class=s> &quot;nested&quot;: {</span>
<span class=s> &quot;one&quot;: 1,</span>
<span class=s> &quot;two&quot;: 2,</span>
<span class=s> &quot;three&quot;: [true, false]</span>
<span class=s> }</span>
<span class=s>}</span><span class=dl>)</span><span class=s>&quot;</span><span class=p>);</span><span class=w></span>
<span class=c1>// access values</span>
<span class=k>auto</span><span class=w> </span><span class=n>val</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>j</span><span class=p>[</span><span class=s>&quot;/&quot;</span><span class=n>_json_pointer</span><span class=p>];</span><span class=w> </span><span class=c1>// {&quot;array&quot;:[&quot;A&quot;,&quot;B&quot;,&quot;C&quot;],...}</span>
<span class=k>auto</span><span class=w> </span><span class=n>val1</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>j</span><span class=p>[</span><span class=s>&quot;/nested/one&quot;</span><span class=n>_json_pointer</span><span class=p>];</span><span class=w> </span><span class=c1>// 1</span>
<span class=k>auto</span><span class=w> </span><span class=n>val2</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>j</span><span class=p>.</span><span class=n>at</span><span class=p>[</span><span class=n>json</span><span class=o>::</span><span class=n>json_pointer</span><span class=p>(</span><span class=s>&quot;/nested/three/1&quot;</span><span class=p>)];</span><span class=w> </span><span class=c1>// false</span>
<span class=k>auto</span><span class=w> </span><span class=n>val3</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>j</span><span class=p>.</span><span class=n>value</span><span class=p>[</span><span class=n>json</span><span class=o>::</span><span class=n>json_pointer</span><span class=p>(</span><span class=s>&quot;/nested/four&quot;</span><span class=p>,</span><span class=w> </span><span class=mi>0</span><span class=p>)];</span><span class=w> </span><span class=c1>// 0</span>
</code></pre></div> <h2 id=flatten-unflatten>Flatten / unflatten<a class=headerlink href=#flatten-unflatten title="Permanent link">&para;</a></h2> <p>The library implements a function <a href=../../api/basic_json/flatten/ ><code>flatten</code></a> to convert any JSON document into a JSON object where each key is a JSON Pointer and each value is a primitive JSON value (i.e., a string, boolean, number, or null).</p> <div class=highlight><pre><span></span><code><span class=c1>// the JSON value from above</span>
<span class=k>auto</span><span class=w> </span><span class=n>j</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>json</span><span class=o>::</span><span class=n>parse</span><span class=p>(</span><span class=sa>R</span><span class=s>&quot;</span><span class=dl>(</span><span class=s>{</span>
<span class=s> &quot;array&quot;: [&quot;A&quot;, &quot;B&quot;, &quot;C&quot;],</span>
<span class=s> &quot;nested&quot;: {</span>
<span class=s> &quot;one&quot;: 1,</span>
<span class=s> &quot;two&quot;: 2,</span>
<span class=s> &quot;three&quot;: [true, false]</span>
<span class=s> }</span>
<span class=s>}</span><span class=dl>)</span><span class=s>&quot;</span><span class=p>);</span><span class=w></span>
<span class=c1>// create flattened value</span>
<span class=k>auto</span><span class=w> </span><span class=n>j_flat</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>j</span><span class=p>.</span><span class=n>flatten</span><span class=p>();</span><span class=w></span>
</code></pre></div> <p>The resulting value <code>j_flat</code> is:</p> <div class=highlight><pre><span></span><code><span class=p>{</span><span class=w></span>
<span class=w> </span><span class=nt>&quot;/array/0&quot;</span><span class=p>:</span><span class=w> </span><span class=s2>&quot;A&quot;</span><span class=p>,</span><span class=w></span>
<span class=w> </span><span class=nt>&quot;/array/1&quot;</span><span class=p>:</span><span class=w> </span><span class=s2>&quot;B&quot;</span><span class=p>,</span><span class=w></span>
<span class=w> </span><span class=nt>&quot;/array/2&quot;</span><span class=p>:</span><span class=w> </span><span class=s2>&quot;C&quot;</span><span class=p>,</span><span class=w></span>
<span class=w> </span><span class=nt>&quot;/nested/one&quot;</span><span class=p>:</span><span class=w> </span><span class=mi>1</span><span class=p>,</span><span class=w></span>
<span class=w> </span><span class=nt>&quot;/nested/two&quot;</span><span class=p>:</span><span class=w> </span><span class=mi>2</span><span class=p>,</span><span class=w></span>
<span class=w> </span><span class=nt>&quot;/nested/three/0&quot;</span><span class=p>:</span><span class=w> </span><span class=kc>true</span><span class=p>,</span><span class=w></span>
<span class=w> </span><span class=nt>&quot;/nested/three/1&quot;</span><span class=p>:</span><span class=w> </span><span class=kc>false</span><span class=w></span>
<span class=p>}</span><span class=w></span>
</code></pre></div> <p>The reverse function, <a href=../../api/basic_json/unflatten/ ><code>unflatten</code></a> recreates the original value.</p> <div class=highlight><pre><span></span><code><span class=k>auto</span><span class=w> </span><span class=n>j_original</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>j_flat</span><span class=p>.</span><span class=n>unflatten</span><span class=p>();</span><span class=w></span>
Deployed 6e36c721f with MkDocs version: 1.4.2
2023-09-23 18:28:29 +03:00
</code></pre></div> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li>Class <a href=../../api/json_pointer/ ><code>json_pointer</code></a></li> <li>Function <a href=../../api/basic_json/flatten/ ><code>flatten</code></a></li> <li>Function <a href=../../api/basic_json/unflatten/ ><code>unflatten</code></a></li> <li><a href=../json_patch/ >JSON Patch</a></li> </ul> <hr> <div class=md-source-file> <small> Last update: <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date">August 10, 2022</span> </small> </div> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var tab,labels=set.querySelector(".tabbed-labels");for(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> </div> <a href=# 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 8v12Z"/></svg> Back to top </a> </main> <footer class=md-footer> <nav class="md-footer__inner md-grid" aria-label=Footer> <a href=../iterators/ class="md-footer__link md-footer__link--prev" aria-label="Previous: Iterators" rel=prev> <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 11h12Z"/></svg> </div> <div class=md-footer__title> <div class=md-ellipsis> <span class=md-footer__direction> Previous </span> Iterators </div> </div> </a> <a href=../json_patch/ class="md-footer__link md-footer__link--next" aria-label="Next: JSON Patch and Diff" rel=next> <div class=md-footer__title> <div class=md-ellipsis> <span class=md-footer__direction> Next </span> JSON Patch and Diff </div> </div> <div class="md-footer__button md-icon"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M4 11v2h12l-5.5 5.5 1.42 1.42L19.84 12l-7.92-7.92L10.5 5.5 16 11H4Z"/></svg> </div> </a> </nav> <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 - 2022 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 0 496 512"><!-- Font Awesome Free 6.2.1 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 2022 Fonticons, Inc.--><path d="M165.9 397.4c0 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 3.6zm-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 2.3zm44.2-1.7c-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-.3-1.9-3-3.2-5.9-2.9zM244.8 8C106.1 8 0 113.3 0 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 12.1C428.2 457.8 496 362.9 496 252 496 113.3 383.5 8 244.8 8zM97.2 352.9c-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-.7-5.2-1.6-1.6-3.9-2.3-5.2-1zm-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-.3-4.3.7zm32.4 35.6c-1.6 1.3-1 4.3 1.3 6.2 2.3 2.3 5.2 2.6 6.5 1 1.3-1.3.7-4.3-1.3-6.2-2.2-2.3-5.2-2.6-6.5-1zm-11.4-14.7c-1.6 1-1.6 3.6 0 5.9 1.6 2.3 4.3 3.3 5.6 2.3 1.6-1.3 1.6-3.9 0-6.2-1.4-2.3-4-3.3-5.
Reference in New Issue Copy Permalink