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57 lines
80 KiB
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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/integration/migration_guide/ rel=canonical><link rel=icon href=../../assets/images/favicon.png><meta name=generator content="mkdocs-1.4.2, mkdocs-material-8.5.10"><title>Migration Guide - 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=#migration-guide 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> Migration Guide </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
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<span class=n>std</span><span class=o>::</span><span class=n>stringstream</span><span class=w> </span><span class=n>ss</span><span class=p>(</span><span class=s>"[1,2,3]"</span><span class=p>);</span><span class=w></span>
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<span class=n>j</span><span class=w> </span><span class=o><<</span><span class=w> </span><span class=n>ss</span><span class=p>;</span><span class=w></span>
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</code></pre></div> </div> <div class=tabbed-block> <div class=highlight><pre><span></span><code><span class=n>nlohmann</span><span class=o>::</span><span class=n>json</span><span class=w> </span><span class=n>j</span><span class=p>;</span><span class=w></span>
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<span class=n>std</span><span class=o>::</span><span class=n>stringstream</span><span class=w> </span><span class=n>ss</span><span class=p>(</span><span class=s>"[1,2,3]"</span><span class=p>);</span><span class=w></span>
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<span class=n>ss</span><span class=w> </span><span class=o>>></span><span class=w> </span><span class=n>j</span><span class=p>;</span><span class=w></span>
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</code></pre></div> </div> </div> </div> </li> <li> <p>Passing iterator pairs or pointer/length pairs to parsing functions (<a href=../../api/basic_json/parse/ ><code>parse</code></a>, <a href=../../api/basic_json/accept/ ><code>accept</code></a>, <a href=../../api/basic_json/sax_parse/ ><code>sax_parse</code></a>, <a href=../../api/basic_json/from_cbor/ ><code>from_cbor</code></a>, <a href=../../api/basic_json/from_msgpack/ ><code>from_msgpack</code></a>, <a href=../../api/basic_json/from_ubjson/ ><code>from_ubjson</code></a>, and <a href=../../api/basic_json/from_bson/ ><code>from_bson</code></a> via initializer lists is deprecated since 3.8.0. Instead, pass two iterators; for instance, call <code>from_cbor(ptr, ptr+len)</code> instead of <code>from_cbor({ptr, len})</code>.</p> <div class="tabbed-set tabbed-alternate" data-tabs=2:2><input checked=checked id=__tabbed_2_1 name=__tabbed_2 type=radio><input id=__tabbed_2_2 name=__tabbed_2 type=radio><div class=tabbed-labels><label for=__tabbed_2_1>Deprecated</label><label for=__tabbed_2_2>Future-proof</label></div> <div class=tabbed-content> <div class=tabbed-block> <div class=highlight><pre><span></span><code><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>s</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=s>"[1,2,3]"</span><span class=p>;</span><span class=w></span>
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<span class=kt>bool</span><span class=w> </span><span class=n>ok</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>accept</span><span class=p>({</span><span class=n>s</span><span class=p>,</span><span class=w> </span><span class=n>s</span><span class=w> </span><span class=o>+</span><span class=w> </span><span class=n>std</span><span class=o>::</span><span class=n>strlen</span><span class=p>(</span><span class=n>s</span><span class=p>)});</span><span class=w></span>
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</code></pre></div> </div> <div class=tabbed-block> <div class=highlight><pre><span></span><code><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>s</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=s>"[1,2,3]"</span><span class=p>;</span><span class=w></span>
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<span class=kt>bool</span><span class=w> </span><span class=n>ok</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>accept</span><span class=p>(</span><span class=n>s</span><span class=p>,</span><span class=w> </span><span class=n>s</span><span class=w> </span><span class=o>+</span><span class=w> </span><span class=n>std</span><span class=o>::</span><span class=n>strlen</span><span class=p>(</span><span class=n>s</span><span class=p>));</span><span class=w></span>
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</code></pre></div> </div> </div> </div> </li> </ul> <h4 id=json-pointers>JSON Pointers<a class=headerlink href=#json-pointers title="Permanent link">¶</a></h4> <ul> <li> <p>Comparing JSON Pointers with strings via <a href=../../api/json_pointer/operator_eq/ ><code>operator==</code></a> and <a href=../../api/json_pointer/operator_ne/ ><code>operator!=</code></a> is deprecated since 3.11.2. To compare a <a href=../../api/json_pointer/ ><code>json_pointer</code></a> <code>p</code> with a string <code>s</code>, convert <code>s</code> to a <code>json_pointer</code> first and use <a href=../../api/json_pointer/operator_eq/ ><code>json_pointer::operator==</code></a> or <a href=../../api/json_pointer/operator_ne/ ><code>json_pointer::operator!=</code></a>.</p> <div class="tabbed-set tabbed-alternate" data-tabs=3:2><input checked=checked id=__tabbed_3_1 name=__tabbed_3 type=radio><input id=__tabbed_3_2 name=__tabbed_3 type=radio><div class=tabbed-labels><label for=__tabbed_3_1>Deprecated</label><label for=__tabbed_3_2>Future-proof</label></div> <div class=tabbed-content> <div class=tabbed-block> <div class=highlight><pre><span></span><code><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=w> </span><span class=n>lhs</span><span class=p>(</span><span class=s>"/foo/bar/1"</span><span class=p>);</span><span class=w></span>
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<span class=n>assert</span><span class=p>(</span><span class=n>lhs</span><span class=w> </span><span class=o>==</span><span class=w> </span><span class=s>"/foo/bar/1"</span><span class=p>);</span><span class=w></span>
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</code></pre></div> </div> <div class=tabbed-block> <div class=highlight><pre><span></span><code><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=w> </span><span class=n>lhs</span><span class=p>(</span><span class=s>"/foo/bar/1"</span><span class=p>);</span><span class=w></span>
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<span class=n>assert</span><span class=p>(</span><span class=n>lhs</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=s>"/foo/bar/1"</span><span class=p>));</span><span class=w></span>
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</code></pre></div> </div> </div> </div> </li> <li> <p>The implicit conversion from JSON Pointers to string (<a href=../../api/json_pointer/operator_string_t/ ><code>json_pointer::operator string_t</code></a>) is deprecated since 3.11.0. Use <a href=../../api/json_pointer/to_string/ ><code>json_pointer::to_string</code></a> instead.</p> <div class="tabbed-set tabbed-alternate" data-tabs=4:2><input checked=checked id=__tabbed_4_1 name=__tabbed_4 type=radio><input id=__tabbed_4_2 name=__tabbed_4 type=radio><div class=tabbed-labels><label for=__tabbed_4_1>Deprecated</label><label for=__tabbed_4_2>Future-proof</label></div> <div class=tabbed-content> <div class=tabbed-block> <div class=highlight><pre><span></span><code><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=w> </span><span class=n>ptr</span><span class=p>(</span><span class=s>"/foo/bar/1"</span><span class=p>);</span><span class=w></span>
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<span class=n>std</span><span class=o>::</span><span class=n>string</span><span class=w> </span><span class=n>s</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>ptr</span><span class=p>;</span><span class=w></span>
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</code></pre></div> </div> <div class=tabbed-block> <div class=highlight><pre><span></span><code><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=w> </span><span class=n>ptr</span><span class=p>(</span><span class=s>"/foo/bar/1"</span><span class=p>);</span><span class=w></span>
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<span class=n>std</span><span class=o>::</span><span class=n>string</span><span class=w> </span><span class=n>s</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>ptr</span><span class=p>.</span><span class=n>to_string</span><span class=p>();</span><span class=w></span>
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</code></pre></div> </div> </div> </div> </li> <li> <p>Passing a <code>basic_json</code> specialization as template parameter <code>RefStringType</code> to <a href=../../api/json_pointer/ ><code>json_pointer</code></a> is deprecated since 3.11.0. The string type can now be directly provided.</p> <div class="tabbed-set tabbed-alternate" data-tabs=5:2><input checked=checked id=__tabbed_5_1 name=__tabbed_5 type=radio><input id=__tabbed_5_2 name=__tabbed_5 type=radio><div class=tabbed-labels><label for=__tabbed_5_1>Deprecated</label><label for=__tabbed_5_2>Future-proof</label></div> <div class=tabbed-content> <div class=tabbed-block> <div class=highlight><pre><span></span><code><span class=k>using</span><span class=w> </span><span class=n>my_json</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>basic_json</span><span class=o><</span><span class=n>std</span><span class=o>::</span><span class=n>map</span><span class=p>,</span><span class=w> </span><span class=n>std</span><span class=o>::</span><span class=n>vector</span><span class=p>,</span><span class=w> </span><span class=n>my_string_type</span><span class=o>></span><span class=p>;</span><span class=w></span>
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<span class=n>nlohmann</span><span class=o>::</span><span class=n>json_pointer</span><span class=o><</span><span class=n>my_json</span><span class=o>></span><span class=w> </span><span class=n>ptr</span><span class=p>(</span><span class=s>"/foo/bar/1"</span><span class=p>);</span><span class=w></span>
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</code></pre></div> </div> <div class=tabbed-block> <div class=highlight><pre><span></span><code><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_pointer</span><span class=o><</span><span class=n>my_string_type</span><span class=o>></span><span class=w> </span><span class=n>ptr</span><span class=p>(</span><span class=s>"/foo/bar/1"</span><span class=p>);</span><span class=w></span>
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</code></pre></div> </div> </div> </div> <p>Thereby, <code>nlohmann::my_json::json_pointer</code> is an alias for <code>nlohmann::json_pointer<my_string_type></code> and is always an alias to the <code>json_pointer</code> with the appropriate string type for all specializations of <code>basic_json</code>.</p> </li> </ul> <h4 id=miscellaneous-functions>Miscellaneous functions<a class=headerlink href=#miscellaneous-functions title="Permanent link">¶</a></h4> <ul> <li> <p>The function <code>iterator_wrapper</code> is deprecated since 3.1.0. Please use the member function <a href=../../api/basic_json/items/ ><code>items</code></a> instead.</p> <div class="tabbed-set tabbed-alternate" data-tabs=6:2><input checked=checked id=__tabbed_6_1 name=__tabbed_6 type=radio><input id=__tabbed_6_2 name=__tabbed_6 type=radio><div class=tabbed-labels><label for=__tabbed_6_1>Deprecated</label><label for=__tabbed_6_2>Future-proof</label></div> <div class=tabbed-content> <div class=tabbed-block> <div class=highlight><pre><span></span><code><span class=k>for</span><span class=w> </span><span class=p>(</span><span class=k>auto</span><span class=w> </span><span class=o>&</span><span class=n>x</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>iterator_wrapper</span><span class=p>(</span><span class=n>j</span><span class=p>))</span><span class=w></span>
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<span class=p>{</span><span class=w></span>
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<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=n>x</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>":"</span><span class=w> </span><span class=o><<</span><span class=w> </span><span class=n>x</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=n>std</span><span class=o>::</span><span class=n>endl</span><span class=p>;</span><span class=w></span>
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<span class=p>}</span><span class=w></span>
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</code></pre></div> </div> <div class=tabbed-block> <div class=highlight><pre><span></span><code><span class=k>for</span><span class=w> </span><span class=p>(</span><span class=k>auto</span><span class=w> </span><span class=o>&</span><span class=n>x</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>items</span><span class=p>())</span><span class=w></span>
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<span class=p>{</span><span class=w></span>
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<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=n>x</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>":"</span><span class=w> </span><span class=o><<</span><span class=w> </span><span class=n>x</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=n>std</span><span class=o>::</span><span class=n>endl</span><span class=p>;</span><span class=w></span>
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<span class=p>}</span><span class=w></span>
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</code></pre></div> </div> </div> </div> </li> <li> <p>Function <code>friend std::ostream& operator>>(const basic_json&, std::ostream&)</code> is deprecated since 3.0.0. Please use <a href=../../api/operator_ltlt/ ><code>friend operator<<(std::ostream&, const basic_json&)</code></a> instead.</p> <div class="tabbed-set tabbed-alternate" data-tabs=7:2><input checked=checked id=__tabbed_7_1 name=__tabbed_7 type=radio><input id=__tabbed_7_2 name=__tabbed_7 type=radio><div class=tabbed-labels><label for=__tabbed_7_1>Deprecated</label><label for=__tabbed_7_2>Future-proof</label></div> <div class=tabbed-content> <div class=tabbed-block> <div class=highlight><pre><span></span><code><span class=n>j</span><span class=w> </span><span class=o>>></span><span class=w> </span><span class=n>std</span><span class=o>::</span><span class=n>cout</span><span class=p>;</span><span class=w></span>
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</code></pre></div> </div> <div class=tabbed-block> <div class=highlight><pre><span></span><code><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=n>j</span><span class=p>;</span><span class=w></span>
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</code></pre></div> </div> </div> </div> </li> <li> <p>The legacy comparison behavior for discarded values is deprecated since 3.11.0. It is already disabled by default and can still be enabled by defining <a href=../../api/macros/json_use_legacy_discarded_value_comparison/ ><code>JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON</code></a> to <code>1</code>.</p> <div class="tabbed-set tabbed-alternate" data-tabs=8:2><input checked=checked id=__tabbed_8_1 name=__tabbed_8 type=radio><input id=__tabbed_8_2 name=__tabbed_8 type=radio><div class=tabbed-labels><label for=__tabbed_8_1>Deprecated</label><label for=__tabbed_8_2>Future-proof</label></div> <div class=tabbed-content> <div class=tabbed-block> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON 1</span>
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<span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json.hpp></span><span class=cp></span>
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</code></pre></div> </div> <div class=tabbed-block> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf><nlohmann/json.hpp></span><span class=cp></span>
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</code></pre></div> </div> </div> </div> </li> </ul> <h2 id=replace-implicit-conversions>Replace implicit conversions<a class=headerlink href=#replace-implicit-conversions title="Permanent link">¶</a></h2> <p>Implicit conversions via <a href=../../api/basic_json/operator_ValueType/ ><code>operator ValueType</code></a> will be switched off by default in the next major release of the library.</p> <p>You can prepare existing code by already defining <a href=../../api/macros/json_use_implicit_conversions/ ><code>JSON_USE_IMPLICIT_CONVERSIONS</code></a> to <code>0</code> and replace any implicit conversions with calls to <a href=../../api/basic_json/get/ ><code>get</code></a>, <a href=../../api/basic_json/get_to/ ><code>get_to</code></a>, <a href=../../api/basic_json/get_ref/ ><code>get_ref</code></a>, or <a href=../../api/basic_json/get_ptr/ ><code>get_ptr</code></a>.</p> <div class="tabbed-set tabbed-alternate" data-tabs=9:3><input checked=checked id=__tabbed_9_1 name=__tabbed_9 type=radio><input id=__tabbed_9_2 name=__tabbed_9 type=radio><input id=__tabbed_9_3 name=__tabbed_9 type=radio><div class=tabbed-labels><label for=__tabbed_9_1>Deprecated</label><label for=__tabbed_9_2>Future-proof</label><label for=__tabbed_9_3>Future-proof (alternative)</label></div> <div class=tabbed-content> <div class=tabbed-block> <div class=highlight><pre><span></span><code><span class=n>nlohmann</span><span class=o>::</span><span class=n>json</span><span class=w> </span><span class=n>j</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=s>"Hello, world!"</span><span class=p>;</span><span class=w></span>
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<span class=n>std</span><span class=o>::</span><span class=n>string</span><span class=w> </span><span class=n>s</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>j</span><span class=p>;</span><span class=w></span>
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</code></pre></div> </div> <div class=tabbed-block> <div class=highlight><pre><span></span><code><span class=n>nlohmann</span><span class=o>::</span><span class=n>json</span><span class=w> </span><span class=n>j</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=s>"Hello, world!"</span><span class=p>;</span><span class=w></span>
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<span class=k>auto</span><span class=w> </span><span class=n>s</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>get</span><span class=o><</span><span class=n>std</span><span class=o>::</span><span class=n>string</span><span class=o>></span><span class=p>();</span><span class=w></span>
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</code></pre></div> </div> <div class=tabbed-block> <div class=highlight><pre><span></span><code><span class=n>nlohmann</span><span class=o>::</span><span class=n>json</span><span class=w> </span><span class=n>j</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=s>"Hello, world!"</span><span class=p>;</span><span class=w></span>
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<span class=n>std</span><span class=o>::</span><span class=n>string</span><span class=w> </span><span class=n>s</span><span class=p>;</span><span class=w></span>
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<span class=n>j</span><span class=p>.</span><span class=n>get_to</span><span class=p>(</span><span class=n>s</span><span class=p>);</span><span class=w></span>
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</code></pre></div> </div> </div> </div> <p>You can prepare existing code by already defining <a href=../../api/macros/json_use_implicit_conversions/ ><code>JSON_USE_IMPLICIT_CONVERSIONS</code></a> to <code>0</code> and replace any implicit conversions with calls to <a href=../../api/basic_json/get/ ><code>get</code></a>.</p> <h2 id=import-namespace-literals-for-udls>Import namespace <code>literals</code> for UDLs<a class=headerlink href=#import-namespace-literals-for-udls title="Permanent link">¶</a></h2> <p>The user-defined string literals <a href=../../api/operator_literal_json/ ><code>operator""_json</code></a> and <a href=../../api/operator_literal_json_pointer/ ><code>operator""_json_pointer</code></a> will be removed from the global namespace in the next major release of the library.</p> <div class="tabbed-set tabbed-alternate" data-tabs=10:2><input checked=checked id=__tabbed_10_1 name=__tabbed_10 type=radio><input id=__tabbed_10_2 name=__tabbed_10 type=radio><div class=tabbed-labels><label for=__tabbed_10_1>Deprecated</label><label for=__tabbed_10_2>Future-proof</label></div> <div class=tabbed-content> <div class=tabbed-block> <div class=highlight><pre><span></span><code><span class=n>nlohmann</span><span class=o>::</span><span class=n>json</span><span class=w> </span><span class=n>j</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=s>"[1,2,3]"</span><span class=n>_json</span><span class=p>;</span><span class=w></span>
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</code></pre></div> </div> <div class=tabbed-block> <div class=highlight><pre><span></span><code><span class=k>using</span><span class=w> </span><span class=k>namespace</span><span class=w> </span><span class=nn>nlohmann</span><span class=o>::</span><span class=nn>literals</span><span class=p>;</span><span class=w></span>
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<span class=n>nlohmann</span><span class=o>::</span><span class=n>json</span><span class=w> </span><span class=n>j</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=s>"[1,2,3]"</span><span class=n>_json</span><span class=p>;</span><span class=w></span>
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</code></pre></div> </div> </div> </div> <p>To prepare existing code, define <a href=../../api/macros/json_use_global_udls/ ><code>JSON_USE_GLOBAL_UDLS</code></a> to <code>0</code> and bring the string literals into scope where needed.</p> <h2 id=do-not-hard-code-the-complete-library-namespace>Do not hard-code the complete library namespace<a class=headerlink href=#do-not-hard-code-the-complete-library-namespace title="Permanent link">¶</a></h2> <p>The <a href=../../features/namespace/ ><code>nlohmann</code> namespace</a> contains a sub-namespace to avoid problems when different versions or configurations of the library are used in the same project. Always use <code>nlohmann</code> as namespace or, when the exact version and configuration is relevant, use macro <a href=../../api/macros/nlohmann_json_namespace/ ><code>NLOHMANN_JSON_NAMESPACE</code></a> to denote the namespace.</p> <div class="tabbed-set tabbed-alternate" data-tabs=11:3><input checked=checked id=__tabbed_11_1 name=__tabbed_11 type=radio><input id=__tabbed_11_2 name=__tabbed_11 type=radio><input id=__tabbed_11_3 name=__tabbed_11 type=radio><div class=tabbed-labels><label for=__tabbed_11_1>Dangerous</label><label for=__tabbed_11_2>Future-proof</label><label for=__tabbed_11_3>Future-proof (alternative)</label></div> <div class=tabbed-content> <div class=tabbed-block> <div class=highlight><pre><span></span><code><span class=kt>void</span><span class=w> </span><span class=nf>to_json</span><span class=p>(</span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json_abi_v3_11_2</span><span class=o>::</span><span class=n>json</span><span class=o>&</span><span class=w> </span><span class=n>j</span><span class=p>,</span><span class=w> </span><span class=k>const</span><span class=w> </span><span class=n>person</span><span class=o>&</span><span class=w> </span><span class=n>p</span><span class=p>)</span><span class=w></span>
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<span class=p>{</span><span class=w></span>
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<span class=w> </span><span class=n>j</span><span class=p>[</span><span class=s>"age"</span><span class=p>]</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>p</span><span class=p>.</span><span class=n>age</span><span class=p>;</span><span class=w></span>
|
||
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<span class=p>}</span><span class=w></span>
|
||
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</code></pre></div> </div> <div class=tabbed-block> <div class=highlight><pre><span></span><code><span class=kt>void</span><span class=w> </span><span class=nf>to_json</span><span class=p>(</span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json</span><span class=o>&</span><span class=w> </span><span class=n>j</span><span class=p>,</span><span class=w> </span><span class=k>const</span><span class=w> </span><span class=n>person</span><span class=o>&</span><span class=w> </span><span class=n>p</span><span class=p>)</span><span class=w></span>
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<span class=p>{</span><span class=w></span>
|
||
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<span class=w> </span><span class=n>j</span><span class=p>[</span><span class=s>"age"</span><span class=p>]</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>p</span><span class=p>.</span><span class=n>age</span><span class=p>;</span><span class=w></span>
|
||
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<span class=p>}</span><span class=w></span>
|
||
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</code></pre></div> </div> <div class=tabbed-block> <div class=highlight><pre><span></span><code><span class=kt>void</span><span class=w> </span><span class=nf>to_json</span><span class=p>(</span><span class=n>NLOHMANN_JSON_NAMESPACE</span><span class=o>::</span><span class=n>json</span><span class=o>&</span><span class=w> </span><span class=n>j</span><span class=p>,</span><span class=w> </span><span class=k>const</span><span class=w> </span><span class=n>person</span><span class=o>&</span><span class=w> </span><span class=n>p</span><span class=p>)</span><span class=w></span>
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<span class=p>{</span><span class=w></span>
|
||
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<span class=w> </span><span class=n>j</span><span class=p>[</span><span class=s>"age"</span><span class=p>]</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>p</span><span class=p>.</span><span class=n>age</span><span class=p>;</span><span class=w></span>
|
||
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<span class=p>}</span><span class=w></span>
|
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</code></pre></div> </div> </div> </div> <h2 id=do-not-use-the-details-namespace>Do not use the <code>details</code> namespace<a class=headerlink href=#do-not-use-the-details-namespace title="Permanent link">¶</a></h2> <p>The <code>details</code> namespace is not part of the public API of the library and can change in any version without announcement. Do not rely on any function or type in the <code>details</code> namespace.</p> <hr> <div class=md-source-file> <small> Last update: <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date">March 8, 2023</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=../ class="md-footer__link md-footer__link--prev" aria-label="Previous: Header only" 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> Header only </div> </div> </a> <a href=../cmake/ class="md-footer__link md-footer__link--next" aria-label="Next: CMake" rel=next> <div class=md-footer__title> <div class=md-ellipsis> <span class=md-footer__direction> Next </span> CMake </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 © 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 0-6.2-1.4-2.3-4-3.3-5.6-2z"/></svg> </a> <a href
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