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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::</span>get <span style="font-size:0.7em; line-height:130%">(std::variant)</span></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>&#23450;&#20041;&#20110;&#22836;&#25991;&#20214; <code><a href="cpp-header-variant.html">&lt;variant&gt;</a></code></div>
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<td rowspan="142">(1)</td>
<td rowspan="142"><span class="t-mark-rev t-since-cxx17">(C++17 &#36215;)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1">&lt;</span> <a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> I, <span class="kw1">class</span>... <span class="me1">Types</span> <span class="sy1">&gt;</span><br /></span>
<p><span class="kw4">constexpr</span> <a href="cpp-utility-variant-variant_alternative.html"><span class="kw1094">std::<span class="me2">variant_alternative_t</span></span></a><span class="sy1">&lt;</span>I, <a href="cpp-utility-variant.html"><span class="kw1085">std::<span class="me2">variant</span></span></a><span class="sy1">&lt;</span>Types...<span class="sy1">&gt;&gt;</span><span class="sy3">&amp;</span><br /></p>
&nbsp; &nbsp; get<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>Types...<span class="sy1">&gt;</span><span class="sy3">&amp;</span> v <span class="br0">)</span><span class="sy4">;</span></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1">&lt;</span> <a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> I, <span class="kw1">class</span>... <span class="me1">Types</span> <span class="sy1">&gt;</span><br /></span>
<p><span class="kw4">constexpr</span> <a href="cpp-utility-variant-variant_alternative.html"><span class="kw1094">std::<span class="me2">variant_alternative_t</span></span></a><span class="sy1">&lt;</span>I, <a href="cpp-utility-variant.html"><span class="kw1085">std::<span class="me2">variant</span></span></a><span class="sy1">&lt;</span>Types...<span class="sy1">&gt;&gt;</span><span class="sy3">&amp;&amp;</span><br /></p>
&nbsp; &nbsp; get<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>Types...<span class="sy1">&gt;</span><span class="sy3">&amp;&amp;</span> v <span class="br0">)</span><span class="sy4">;</span></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1">&lt;</span> <a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> I, <span class="kw1">class</span>... <span class="me1">Types</span> <span class="sy1">&gt;</span><br /></span>
<p><span class="kw4">constexpr</span> <span class="kw4">const</span> <a href="cpp-utility-variant-variant_alternative.html"><span class="kw1094">std::<span class="me2">variant_alternative_t</span></span></a><span class="sy1">&lt;</span>I, <a href="cpp-utility-variant.html"><span class="kw1085">std::<span class="me2">variant</span></span></a><span class="sy1">&lt;</span>Types...<span class="sy1">&gt;&gt;</span><span class="sy3">&amp;</span><br /></p>
&nbsp; &nbsp; get<span class="br0">(</span> <span class="kw4">const</span> <a href="cpp-utility-variant.html"><span class="kw1085">std::<span class="me2">variant</span></span></a><span class="sy1">&lt;</span>Types...<span class="sy1">&gt;</span><span class="sy3">&amp;</span> v <span class="br0">)</span><span class="sy4">;</span></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1">&lt;</span> <a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> I, <span class="kw1">class</span>... <span class="me1">Types</span> <span class="sy1">&gt;</span><br /></span>
<p><span class="kw4">constexpr</span> <span class="kw4">const</span> <a href="cpp-utility-variant-variant_alternative.html"><span class="kw1094">std::<span class="me2">variant_alternative_t</span></span></a><span class="sy1">&lt;</span>I, <a href="cpp-utility-variant.html"><span class="kw1085">std::<span class="me2">variant</span></span></a><span class="sy1">&lt;</span>Types...<span class="sy1">&gt;&gt;</span><span class="sy3">&amp;</span><br /></p>
&nbsp; &nbsp; get<span class="br0">(</span> <span class="kw4">const</span> <a href="cpp-utility-variant.html"><span class="kw1085">std::<span class="me2">variant</span></span></a><span class="sy1">&lt;</span>Types...<span class="sy1">&gt;</span><span class="sy3">&amp;&amp;</span> v <span class="br0">)</span><span class="sy4">;</span></div>
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<td rowspan="142">(2)</td>
<td rowspan="142"><span class="t-mark-rev t-since-cxx17">(C++17 &#36215;)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1">&lt;</span> <span class="kw1">class</span> T, <span class="kw1">class</span>... <span class="me1">Types</span> <span class="sy1">&gt;</span><br />
<span class="kw4">constexpr</span> T<span class="sy3">&amp;</span> get<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>Types...<span class="sy1">&gt;</span><span class="sy3">&amp;</span> v <span class="br0">)</span><span class="sy4">;</span></span></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1">&lt;</span> <span class="kw1">class</span> T, <span class="kw1">class</span>... <span class="me1">Types</span> <span class="sy1">&gt;</span><br />
<span class="kw4">constexpr</span> T<span class="sy3">&amp;&amp;</span> get<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>Types...<span class="sy1">&gt;</span><span class="sy3">&amp;&amp;</span> v <span class="br0">)</span><span class="sy4">;</span></span></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1">&lt;</span> <span class="kw1">class</span> T, <span class="kw1">class</span>... <span class="me1">Types</span> <span class="sy1">&gt;</span><br />
<span class="kw4">constexpr</span> <span class="kw4">const</span> T<span class="sy3">&amp;</span> get<span class="br0">(</span> <span class="kw4">const</span> <a href="cpp-utility-variant.html"><span class="kw1085">std::<span class="me2">variant</span></span></a><span class="sy1">&lt;</span>Types...<span class="sy1">&gt;</span><span class="sy3">&amp;</span> v <span class="br0">)</span><span class="sy4">;</span></span></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1">&lt;</span> <span class="kw1">class</span> T, <span class="kw1">class</span>... <span class="me1">Types</span> <span class="sy1">&gt;</span><br />
<span class="kw4">constexpr</span> <span class="kw4">const</span> T<span class="sy3">&amp;&amp;</span> get<span class="br0">(</span> <span class="kw4">const</span> <a href="cpp-utility-variant.html"><span class="kw1085">std::<span class="me2">variant</span></span></a><span class="sy1">&lt;</span>Types...<span class="sy1">&gt;</span><span class="sy3">&amp;&amp;</span> v <span class="br0">)</span><span class="sy4">;</span></span></div>
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<div class="t-li1"><span class="t-li">1)</span> &#22522;&#20110;&#19979;&#26631;&#30340;&#20540;&#35775;&#38382;&#22120;&#65306;&#33509; <span class="t-c"><span class="mw-geshi cpp source-cpp">v.<span class="me1">index</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1">==</span> I</span></span> &#65292;&#21017;&#36820;&#22238;&#21040;&#23384;&#20648;&#20110; <code>v</code> &#30340;&#20540;&#30340;&#24341;&#29992;&#12290;&#21542;&#21017;&#25243;&#20986; <span class="t-lc"><a href="cpp-utility-variant-bad_variant_access.html">std::bad_variant_access</a></span> &#12290;&#33509; <code>I</code> &#19981;&#26159; <code>varian</code> &#30340;&#21512;&#27861;&#19979;&#26631;&#65292;&#21017;&#27492;&#35843;&#29992;&#20026;&#30149;&#24335;&#12290;</div>
<div class="t-li1"><span class="t-li">2)</span> &#22522;&#20110;&#31867;&#22411;&#30340;&#20540;&#35775;&#38382;&#22120;&#65306;&#33509; <span class="t-c"><span class="mw-geshi cpp source-cpp">v</span></span> &#20445;&#26377;&#21487;&#36873;&#39033; <code>T</code> &#65292;&#21017;&#36820;&#22238;&#21040;&#23384;&#20648;&#20110; <code>v</code> &#30340;&#20540;&#30340;&#24341;&#29992;&#12290;&#21542;&#21017;&#25243;&#20986; <span class="t-lc"><a href="cpp-utility-variant-bad_variant_access.html">std::bad_variant_access</a></span> &#12290;&#33509; <code>T</code> &#19981;&#26159; <code>Types...</code> &#20013;&#21807;&#19968;&#23384;&#22312;&#30340;&#20803;&#32032;&#65292;&#21017;&#27492;&#35843;&#29992;&#20026;&#30149;&#24335;&#12290;</div>
<h3><span class="mw-headline" id=".E6.A8.A1.E6.9D.BF.E5.BD.A2.E5.8F.82">&#27169;&#26495;&#24418;&#21442;</span></h3>
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<td>I</td>
<td>-</td>
<td>&#35201;&#26597;&#25214;&#30340;&#19979;&#26631;</td>
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<td>T</td>
<td>-</td>
<td>&#35201;&#26597;&#25214;&#30340;&#21807;&#19968;&#31867;&#22411;</td>
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<td>Types...</td>
<td>-</td>
<td>&#26500;&#25104; <code>variant</code> &#30340;&#31867;&#22411;</td>
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<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">&#21442;&#25968;</span></h3>
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<td>v</td>
<td>-</td>
<td>&#19968;&#20010; <code>variant</code></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>&#21040;&#23384;&#20648;&#20110; <code>variant</code> &#20013;&#30340;&#20540;&#30340;&#24341;&#29992;&#12290;</p>
<h3><span class="mw-headline" id=".E5.BC.82.E5.B8.B8">&#24322;&#24120;</span></h3>
<div class="t-li1"><span class="t-li">1,2)</span> &#38169;&#35823;&#26102;&#25243; <span class="t-lc"><a href="cpp-utility-variant-bad_variant_access.html">std::bad_variant_access</a></span> &#12290;</div>
<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">&#31034;&#20363;</span></h3>
<div class="t-example">
<div class="t-example-live-link"></div>
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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="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>, <span class="kw4">float</span><span class="sy1">&gt;</span> v<span class="br0">{</span><span class="nu0">12</span><span class="br0">}</span>, w<span class="sy4">;</span>
<span class="kw4">int</span> i <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">get</span><span class="sy1">&lt;</span><span class="kw4">int</span><span class="sy1">&gt;</span><span class="br0">(</span>v<span class="br0">)</span><span class="sy4">;</span>
w <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">get</span><span class="sy1">&lt;</span><span class="kw4">int</span><span class="sy1">&gt;</span><span class="br0">(</span>v<span class="br0">)</span><span class="sy4">;</span>
w <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">get</span><span class="sy1">&lt;</span><span class="nu0">0</span><span class="sy1">&gt;</span><span class="br0">(</span>v<span class="br0">)</span><span class="sy4">;</span> <span class="co1">// &#25928;&#26524;&#21516;&#21069;&#19968;&#34892;</span>
<span class="co1">// std::get&lt;double&gt;(v); // &#38169;&#35823;&#65306; [int, float] &#20013;&#26080; double</span>
<span class="co1">// std::get&lt;3&gt;(v); // &#38169;&#35823;&#65306;&#21512;&#27861;&#30340; index &#20540;&#26159; 0 &#21644; 1</span>
<span class="kw1">try</span> <span class="br0">{</span>
std<span class="sy4">::</span><span class="me2">get</span><span class="sy1">&lt;</span><span class="kw4">float</span><span class="sy1">&gt;</span><span class="br0">(</span>w<span class="br0">)</span><span class="sy4">;</span> <span class="co1">// w &#21547;&#26377; int &#65292;&#38750; float &#65306;&#23558;&#25243;&#20986;&#24322;&#24120;</span>
<span class="br0">}</span>
<span class="kw1">catch</span> <span class="br0">(</span><a href="cpp-utility-variant-bad_variant_access.html"><span class="kw1089">std::<span class="me2">bad_variant_access</span></span></a><span class="sy3">&amp;</span><span class="br0">)</span> <span class="br0">{</span><span class="br0">}</span>
<span class="br0">}</span></pre></div>
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<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">&#21442;&#38405;</span></h3>
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<div class="t-dsc-member-div">
<div><a href="cpp-utility-variant-get_if.html"><span class="t-lines"><span>get_if</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx17">(C++17)</span></span></span></div>
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<td>&#20197;&#32473;&#23450;&#32034;&#24341;&#25110;&#31867;&#22411;&#65288;&#33509;&#20854;&#21807;&#19968;&#65289;&#65292;&#33719;&#24471;&#25351;&#21521;&#34987;&#25351;&#21521;&#30340; variant &#30340;&#20540;&#30340;&#25351;&#38024;&#65292;&#38169;&#35823;&#26102;&#36820;&#22238;&#31354;&#25351;&#38024;<br />
<span class="t-mark">(&#20989;&#25968;&#27169;&#26495;)</span></td>
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<div class="t-dsc-member-div">
<div><a href="cpp-utility-tuple-get.html"><span class="t-lines"><span>std::get<span class="t-dsc-small">(std::tuple)</span></span></span></a></div>
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<td>&#20803;&#32452;&#24335;&#35775;&#38382;&#25351;&#23450;&#30340;&#20803;&#32032;<br />
<span class="t-mark">(&#20989;&#25968;&#27169;&#26495;)</span></td>
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<div class="t-dsc-member-div">
<div><a href="cpp-container-array-get.html"><span class="t-lines"><span>std::get<span class="t-dsc-small">(std::array)</span></span></span></a></div>
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<td>&#35775;&#38382; <code>array</code> &#30340;&#19968;&#20010;&#20803;&#32032;<br />
<span class="t-mark">(&#20989;&#25968;&#27169;&#26495;)</span></td>
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<div class="t-dsc-member-div">
<div><a href="cpp-utility-pair-get.html"><span class="t-lines"><span>std::get<span class="t-dsc-small">(std::pair)</span></span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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<td>&#35775;&#38382; <code>pair</code> &#30340;&#19968;&#20010;&#20803;&#32032;<br />
<span class="t-mark">(&#20989;&#25968;&#27169;&#26495;)</span></td>
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