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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::variant&lt;Types...&gt;::</span>swap</h1>
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<div id="contentSub"><span class="subpages">&lt; <a href="cpp.html">cpp</a>&lrm; | <a href="cpp-utility.html">utility</a>&lrm; | <a href="cpp-utility-variant.html">variant</a></span></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">void</span> swap<span class="br0">(</span> variant<span class="sy3">&amp;</span> rhs <span class="br0">)</span> <span class="kw1">noexcept</span><span class="br0">(</span><span class="coMULTI">/* see below */</span><span class="br0">)</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx17">(C++17 &#36215;)</span><br />
<span class="t-mark-rev t-until-cxx20">(C++20 &#21069;)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> <span class="kw4">void</span> swap<span class="br0">(</span> variant<span class="sy3">&amp;</span> rhs <span class="br0">)</span> <span class="kw1">noexcept</span><span class="br0">(</span><span class="coMULTI">/* see below */</span><span class="br0">)</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 &#36215;)</span></td>
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<p>&#20132;&#25442;&#20108;&#20010; <code>variant</code> &#23545;&#35937;&#12290;</p>
<ul>
<li>&#33509; <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this</span></span> &#21644; <code>rhs</code> &#22343;<a href="cpp-utility-variant-valueless_by_exception.html">&#22240;&#24322;&#24120;&#26080;&#20540;</a>&#65292;&#21017;&#19981;&#20570;&#20219;&#20309;&#20107;&#65307;</li>
<li>&#21542;&#21017;&#65292;&#33509; <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this</span></span> &#19982; <code>rhs</code> &#20445;&#26377;&#21516;&#19968;&#21487;&#36873;&#39033;&#65292;&#21017;&#35843;&#29992; <span class="t-c"><span class="mw-geshi cpp source-cpp">swap<span class="br0">(</span>std<span class="sy4">::</span><span class="me2">get</span><span class="sy1">&lt;</span>i<span class="sy1">&gt;</span><span class="br0">(</span><span class="sy2">*</span>this<span class="br0">)</span>, std<span class="sy4">:</span>get<span class="sy1">&lt;</span>i<span class="sy1">&gt;</span><span class="br0">(</span>rhs<span class="br0">)</span><span class="br0">)</span></span></span> &#65292;&#20854;&#20013; <code>i</code> &#31561;&#20110; <code>index()</code> &#12290;&#33509;&#25243;&#20986;&#24322;&#24120;&#65292;&#21017;&#20540;&#30340;&#29366;&#24577;&#20381;&#36182;&#20110;&#34987;&#35843;&#29992;&#20132;&#25442;&#20989;&#25968;&#30340;&#24322;&#24120;&#23433;&#20840;&#65307;</li>
<li>&#21542;&#21017;&#65292;&#20132;&#25442; <code>rhs</code> &#19982; <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this</span></span> &#30340;&#20540;&#12290;&#33509;&#25243;&#20986;&#24322;&#24120;&#65292;&#21017; <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this</span></span> &#19982; <code>rhs</code> &#30340;&#29366;&#24577;&#20381;&#36182;&#20110; <code>variant</code> &#31227;&#21160;&#26500;&#36896;&#20989;&#25968;&#30340;&#24322;&#24120;&#23433;&#20840;&#12290;</li>
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<p>&#38500;&#38750;&#23545;&#20110;&#25152;&#26377; <code>Types...</code> &#20013;&#30340; <code>T_i</code> &#65292; <code>T_i</code> &#24038;&#20540;<a href="cpp-named_req-Swappable.html"><span style="font-style:italic">&#21487;&#20132;&#25442;</span> <span style="font-family: Georgia, &#39;DejaVu Serif&#39;, serif; font-style:italic">(Swappable)</span></a> &#19988; <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-types-is_move_constructible.html"><span class="kw539">std::<span class="me2">is_move_constructible_v</span></span></a><span class="sy1">&lt;</span>T_i<span class="sy1">&gt;</span></span></span> &#20026; <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">true</span></span></span> &#65292;&#21542;&#21017;&#34892;&#20026;&#26410;&#23450;&#20041;&#12290;</p>
<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">&#21442;&#25968;</span></h3>
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<td>rhs</td>
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<td>&#35201;&#20132;&#25442;&#30340; <code>variant</code> &#23545;&#35937;</td>
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<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">&#36820;&#22238;&#20540;</span></h3>
<p>&#65288;&#26080;&#65289;</p>
<h3><span class="mw-headline" id=".E5.BC.82.E5.B8.B8">&#24322;&#24120;</span></h3>
<p>&#33509; <span class="t-c"><span class="mw-geshi cpp source-cpp">this<span class="sy2">-</span><span class="sy1">&gt;</span>index<span class="br0">(</span><span class="br0">)</span> <span class="sy1">==</span> rhs.<span class="me1">index</span><span class="br0">(</span><span class="br0">)</span></span></span> &#65292;&#21017;&#21487;&#33021;&#25243;&#20986;&#20219;&#20309; <span class="t-c"><span class="mw-geshi cpp source-cpp">swap<span class="br0">(</span>std<span class="sy4">::</span><span class="me2">get</span><span class="sy1">&lt;</span>i<span class="sy1">&gt;</span><span class="br0">(</span><span class="sy2">*</span>this<span class="br0">)</span>, std<span class="sy4">::</span><span class="me2">get</span><span class="sy1">&lt;</span>i<span class="sy1">&gt;</span><span class="br0">(</span>rhs<span class="br0">)</span><span class="br0">)</span></span></span> &#25152;&#25243;&#30340;&#24322;&#24120;&#65292;&#20854;&#20013; <code>i</code> &#31561;&#20110; <span class="t-c"><span class="mw-geshi cpp source-cpp">index<span class="br0">(</span><span class="br0">)</span></span></span> &#12290;</p>
<p>&#21542;&#21017;&#65292;&#21487;&#33021;&#25243;&#20986;&#20219;&#20309;&#24403;&#21069; <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this</span></span> &#19982; <span class="t-c"><span class="mw-geshi cpp source-cpp">rhs</span></span> &#25152;&#20445;&#26377;&#30340;&#21487;&#36873;&#39033;&#30340;&#31227;&#21160;&#26500;&#36896;&#20989;&#25968;&#25152;&#25243;&#30340;&#24322;&#24120;&#12290;</p>
<div class="t-noexcept-full"><a href="cpp-language-noexcept_spec.html"><tt>noexcept</tt></a> &#35828;&#26126;&#65306;&nbsp;&nbsp;
<div class="t-noexcept-box"><span class="t-cc"><span class="mw-geshi cpp source-cpp"><span class="kw1">noexcept</span><span class="br0">(</span><span class="br0">(</span><span class="br0">(</span><a href="cpp-types-is_move_constructible.html"><span class="kw543">std::<span class="me2">is_nothrow_move_constructible_v</span></span></a><span class="sy1">&lt;</span>Types<span class="sy1">&gt;</span> <span class="sy3">&amp;&amp;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<a href="cpp-types-is_swappable.html"><span class="kw577">std::<span class="me2">is_nothrow_swappable_v</span></span></a><span class="sy1">&lt;</span>Types<span class="sy1">&gt;</span><span class="br0">)</span> <span class="sy3">&amp;&amp;</span> ...<span class="br0">)</span><span class="br0">)</span></span></span></div>
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<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">&#31034;&#20363;</span></h3>
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<pre class="de1"><span class="co2">#include &lt;variant&gt;</span>
<span class="co2">#include &lt;string&gt;</span>
<span class="co2">#include &lt;iostream&gt;</span>
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
<span class="br0">{</span>
<a href="cpp-utility-variant.html"><span class="kw1085">std::<span class="me2">variant</span></span></a><span class="sy1">&lt;</span><span class="kw4">int</span>, <a href="cpp-string-basic_string.html"><span class="kw1230">std::<span class="me2">string</span></span></a><span class="sy1">&gt;</span> v1<span class="br0">{</span><span class="nu0">2</span><span class="br0">}</span>, v2<span class="br0">{</span><span class="st0">&quot;abc&quot;</span><span class="br0">}</span><span class="sy4">;</span>
<a href="cpp-utility-variant-visit.html"><span class="kw1086">std::<span class="me2">visit</span></span></a><span class="br0">(</span><span class="br0">[</span><span class="br0">]</span> <span class="br0">(</span><span class="kw4">auto</span><span class="sy3">&amp;&amp;</span> x<span class="br0">)</span> <span class="br0">{</span> <a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> x <span class="sy1">&lt;&lt;</span> <span class="st0">&#39; &#39;</span><span class="sy4">;</span> <span class="br0">}</span>, v1<span class="br0">)</span><span class="sy4">;</span>
<a href="cpp-utility-variant-visit.html"><span class="kw1086">std::<span class="me2">visit</span></span></a><span class="br0">(</span><span class="br0">[</span><span class="br0">]</span> <span class="br0">(</span><span class="kw4">auto</span><span class="sy3">&amp;&amp;</span> x<span class="br0">)</span> <span class="br0">{</span> <a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> x <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span><span class="sy4">;</span> <span class="br0">}</span>, v2<span class="br0">)</span><span class="sy4">;</span>
v1.<span class="me1">swap</span><span class="br0">(</span>v2<span class="br0">)</span><span class="sy4">;</span>
<a href="cpp-utility-variant-visit.html"><span class="kw1086">std::<span class="me2">visit</span></span></a><span class="br0">(</span><span class="br0">[</span><span class="br0">]</span> <span class="br0">(</span><span class="kw4">auto</span><span class="sy3">&amp;&amp;</span> x<span class="br0">)</span> <span class="br0">{</span> <a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> x <span class="sy1">&lt;&lt;</span> <span class="st0">&#39; &#39;</span><span class="sy4">;</span> <span class="br0">}</span>, v1<span class="br0">)</span><span class="sy4">;</span>
<a href="cpp-utility-variant-visit.html"><span class="kw1086">std::<span class="me2">visit</span></span></a><span class="br0">(</span><span class="br0">[</span><span class="br0">]</span> <span class="br0">(</span><span class="kw4">auto</span><span class="sy3">&amp;&amp;</span> x<span class="br0">)</span> <span class="br0">{</span> <a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> x <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span><span class="sy4">;</span> <span class="br0">}</span>, v2<span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span></pre></div>
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<p>&#36755;&#20986;&#65306;</p>
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<pre class="de1">2 abc
abc 2</pre></div>
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<h3><span class="mw-headline" id=".E7.BC.BA.E9.99.B7.E6.8A.A5.E5.91.8A">&#32570;&#38519;&#25253;&#21578;</span></h3>
<p>&#19979;&#21015;&#26356;&#25913;&#34892;&#20026;&#30340;&#32570;&#38519;&#25253;&#21578;&#36861;&#28335;&#22320;&#24212;&#29992;&#20110;&#20197;&#21069;&#20986;&#29256;&#30340; C++ &#26631;&#20934;&#12290;</p>
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<th>DR</th>
<th>&#24212;&#29992;&#20110;</th>
<th>&#20986;&#29256;&#26102;&#30340;&#34892;&#20026;</th>
<th>&#27491;&#30830;&#34892;&#20026;</th>
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<td><a rel="nofollow" class="external text" href="https://wg21.link/P2231R1">P2231R1</a></td>
<td>C++20</td>
<td><code>swap</code> &#19981;&#26159; constexpr &#65292;&#32780;&#35201;&#27714;&#30340;&#25805;&#20316;&#22312; C++20 &#20013;&#33021;&#20026; constexpr</td>
<td>&#20351;&#20043;&#20026; constexpr</td>
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