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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::</span>bad_variant_access</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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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">class</span> bad_variant_access <span class="sy4">:</span> <span class="kw1">public</span> <a href="cpp-error-exception.html"><span class="kw764">std::<span class="me2">exception</span></span></a></span></div>
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<td><span class="t-mark-rev t-since-cxx17">(C++17 &#36215;)</span></td>
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<p><code>std::bad_variant_access</code> &#26159;&#19979;&#21015;&#24773;&#24418;&#20013;&#25243;&#20986;&#30340;&#24322;&#24120;&#31867;&#22411;&#65306;</p>
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<li>&#20197;&#19981;&#21305;&#37197;&#24403;&#21069;&#27963;&#36291;&#21487;&#36873;&#39033;&#30340;&#19979;&#26631;&#25110;&#31867;&#22411;&#35843;&#29992; <a href="cpp-utility-variant-get.html"><tt>std::get<span style="font-size:0.7em; line-height:130%">(std::variant)</span></tt></a></li>
<li>&#35843;&#29992; <a href="cpp-utility-variant-visit.html"><tt>std::visit</tt></a> &#35266;&#35272;&#22240;&#24322;&#24120;&#26080;&#20540; (<a href="cpp-utility-variant-valueless_by_exception.html"><tt>valueless_by_exception</tt></a>) &#30340; <code>variant</code></li>
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<h3><span class="mw-headline" id=".E6.88.90.E5.91.98.E5.87.BD.E6.95.B0">&#25104;&#21592;&#20989;&#25968;</span></h3>
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<div><span class="t-lines"><span>(&#26500;&#36896;&#20989;&#25968;)</span></span></div>
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<td>&#26500;&#36896;&#26032;&#30340; <code>bad_variant_access</code> &#23545;&#35937;<br />
<span class="t-mark">(&#20844;&#24320;&#25104;&#21592;&#20989;&#25968;)</span></td>
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<div><span class="t-lines"><span>operator=</span></span></div>
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<td>&#26367;&#25442; <code>bad_variant_access</code> &#23545;&#35937;<br />
<span class="t-mark">(&#20844;&#24320;&#25104;&#21592;&#20989;&#25968;)</span></td>
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<div><span class="t-lines"><span>what</span></span></div>
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<td>&#36820;&#22238;&#35299;&#37322;&#23383;&#31526;&#20018;<br />
<span class="t-mark">(&#20844;&#24320;&#25104;&#21592;&#20989;&#25968;)</span></td>
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<h2><span class="mw-headline" id="std::bad_variant_access::bad_variant_access"><span style="font-size:0.7em; line-height:130%">std::bad_variant_access::</span>bad_variant_access</span></h2>
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<div><span class="mw-geshi cpp source-cpp">bad_variant_access<span class="br0">(</span><span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span></span></div>
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<td>(1)</td>
<td><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">bad_variant_access<span class="br0">(</span> <span class="kw4">const</span> bad_variant_access<span class="sy3">&amp;</span> other <span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span></span></div>
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<td>(2)</td>
<td><span class="t-mark-rev t-since-cxx17">(C++17 &#36215;)</span></td>
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<p>&#26500;&#36896;&#26032;&#30340;&#25317;&#26377;&#23454;&#29616;&#23450;&#20041;&#30340;&#31354;&#32456;&#27490;&#23383;&#33410;&#23383;&#31526;&#20018;&#30340; <code>bad_variant_access</code> &#23545;&#35937;&#65292;&#23383;&#31526;&#20018;&#33021;&#36890;&#36807; <a href="cpp-error-exception-what.html"><tt>what()</tt></a> &#35775;&#38382;&#12290;</p>
<div class="t-li1"><span class="t-li">1)</span> &#40664;&#35748;&#26500;&#36896;&#20989;&#25968;&#12290;</div>
<div class="t-li1"><span class="t-li">2)</span> &#22797;&#21046;&#26500;&#36896;&#20989;&#25968;&#12290;&#33509; <code>*this</code> &#19982; <code>other</code> &#22343;&#25317;&#26377;&#21160;&#24577;&#31867;&#22411; <code>std::bad_variant_access</code> &#21017; <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-string-byte-strcmp.html"><span class="kw1145">std::<span class="me2">strcmp</span></span></a><span class="br0">(</span>what<span class="br0">(</span><span class="br0">)</span>, other.<span class="me1">what</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span> <span class="sy1">==</span> <span class="nu0">0</span></span></span> &#12290;</div>
<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">&#21442;&#25968;</span></h3>
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<td>other</td>
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<td>&#35201;&#22797;&#21046;&#30340;&#21478;&#19968;&#24322;&#24120;&#23545;&#35937;</td>
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<h2><span class="mw-headline" id="std::bad_variant_access::operator.3D"><span style="font-size:0.7em; line-height:130%">std::bad_variant_access::</span>operator=</span></h2>
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<div><span class="mw-geshi cpp source-cpp">bad_variant_access<span class="sy3">&amp;</span> operator<span class="sy1">=</span><span class="br0">(</span> <span class="kw4">const</span> bad_variant_access<span class="sy3">&amp;</span> other <span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx17">(C++17 &#36215;)</span></td>
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<p>&#20197; <code>other</code> &#30340;&#20869;&#23481;&#36171;&#20540;&#12290;&#33509; <code>*this</code> &#19982; <code>other</code> &#22343;&#25317;&#26377;&#21160;&#24577;&#31867;&#22411; <code>std::bad_variant_access</code> &#21017;&#36171;&#20540;&#21518; <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-string-byte-strcmp.html"><span class="kw1145">std::<span class="me2">strcmp</span></span></a><span class="br0">(</span>what<span class="br0">(</span><span class="br0">)</span>, other.<span class="me1">what</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span> <span class="sy1">==</span> <span class="nu0">0</span></span></span> &#12290;</p>
<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0_2">&#21442;&#25968;</span></h3>
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<td>other</td>
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<td>&#29992;&#20197;&#36171;&#20540;&#30340;&#21478;&#19968;&#24322;&#24120;&#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><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this</span></span></p>
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<h2><span class="mw-headline" id="std::bad_variant_access::what"><span style="font-size:0.7em; line-height:130%">std::bad_variant_access::</span>what</span></h2>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">virtual</span> <span class="kw4">const</span> <span class="kw4">char</span><span class="sy2">*</span> what<span class="br0">(</span><span class="br0">)</span> <span class="kw4">const</span> <span class="kw1">noexcept</span><span class="sy4">;</span></span></div>
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<td class="t-dcl-nopad"></td>
<td><span class="t-mark-rev t-since-cxx17">(C++17 &#36215;)</span></td>
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<p>&#36820;&#22238;&#35299;&#37322;&#23383;&#31526;&#20018;&#12290;</p>
<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0_3">&#21442;&#25968;</span></h3>
<p>&#65288;&#26080;&#65289;</p>
<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC_2">&#36820;&#22238;&#20540;</span></h3>
<p>&#25351;&#21521;&#26377;&#35299;&#37322;&#20449;&#24687;&#30340;&#31354;&#32456;&#27490;&#23383;&#31526;&#20018;&#30340;&#25351;&#38024;&#12290;&#35813;&#23383;&#31526;&#20018;&#36866;&#21512;&#36716;&#25442;&#24182;&#26174;&#31034;&#20026; <span class="t-lc"><a href="cpp-string-basic_string.html">std::wstring</a></span> &#12290;&#20445;&#35777;&#35813;&#25351;&#38024;&#33267;&#23569;&#21040;&#33719;&#24471;&#23427;&#26469;&#28304;&#30340;&#24322;&#24120;&#23545;&#35937;&#34987;&#38144;&#27585;&#65292;&#25110;&#22312;&#35813;&#24322;&#24120;&#23545;&#35937;&#19978;&#35843;&#29992;&#38750; const &#25104;&#21592;&#20989;&#25968;&#65288;&#20363;&#22914;&#22797;&#21046;&#36171;&#20540;&#36816;&#31639;&#31526;&#65289;&#20026;&#27490;&#21512;&#27861;&#12290;</p>
<h3><span class="mw-headline" id=".E6.B3.A8.E8.A7.A3">&#27880;&#35299;</span></h3>
<p>&#20801;&#35768;&#20294;&#19981;&#35201;&#27714;&#23454;&#29616;&#35206;&#20889; <code>what()</code> &#12290;</p>
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<div class="t-inherited">
<h2><span class="mw-headline" id=".E7.BB.A7.E6.89.BF.E8.87.AA_std::exception">&#32487;&#25215;&#33258; <a href="cpp-error-exception.html"><span style="font-size:0.7em; line-height:130%">std::</span>exception</a></span></h2>
<h3><span class="mw-headline" id=".E6.88.90.E5.91.98.E5.87.BD.E6.95.B0_2">&#25104;&#21592;&#20989;&#25968;</span></h3>
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<div class="t-dsc-member-div t-dsc-member-nobold-div">
<div><a href="cpp-error-exception-~exception.html"><span class="t-lines"><span>(&#26512;&#26500;&#20989;&#25968;)</span></span></a></div>
<div><span class="t-lines"><span><span class="t-cmark">[&#34394;]</span></span></span></div>
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<td>&#26512;&#26500;&#35813;&#24322;&#24120;&#23545;&#35937;<br />
<span class="t-mark">(<code>std::exception</code> &#30340;&#34394;&#20844;&#24320;&#25104;&#21592;&#20989;&#25968;)</span></td>
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<div class="t-dsc-member-div">
<div><a href="cpp-error-exception-what.html"><span class="t-lines"><span>what</span></span></a></div>
<div><span class="t-lines"><span><span class="t-cmark">[&#34394;]</span></span></span></div>
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<td>&#36820;&#22238;&#35299;&#37322;&#24615;&#23383;&#31526;&#20018;<br />
<span class="t-mark">(<code>std::exception</code> &#30340;&#34394;&#20844;&#24320;&#25104;&#21592;&#20989;&#25968;)</span></td>
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<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">&#31034;&#20363;</span></h3>
<div class="t-example">
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<div class="cpp source-cpp">
<pre class="de1"><span class="co2">#include &lt;variant&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>, <span class="kw4">float</span><span class="sy1">&gt;</span> v<span class="sy4">;</span>
v <span class="sy1">=</span> <span class="nu0">12</span><span class="sy4">;</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>v<span class="br0">)</span><span class="sy4">;</span>
<span class="br0">}</span>
<span class="kw1">catch</span><span class="br0">(</span><span class="kw4">const</span> std<span class="sy4">::</span><span class="me2">bad_variant_access</span><span class="sy3">&amp;</span> e<span class="br0">)</span> <span class="br0">{</span>
<a href="cpp-io-cout.html"><span class="kw1757">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> e.<span class="me1">what</span><span class="br0">(</span><span class="br0">)</span> <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>
<span class="br0">}</span></pre></div>
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<p>&#21487;&#33021;&#30340;&#36755;&#20986;&#65306;</p>
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<div class="text source-text">
<pre class="de1">bad_variant_access</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><a href="cpp-utility-variant-get.html"><span class="t-lines"><span>std::get<span class="t-dsc-small">(std::variant)</span></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;&#31867;&#22411;&#21807;&#19968;&#65289;&#35835;&#21462; <code>variant</code> &#30340;&#20540;&#65292;&#38169;&#35823;&#26102;&#25243;&#20986;&#24322;&#24120;<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-variant-visit.html"><span class="t-lines"><span>visit</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;&#19968;&#25110;&#22810;&#20010; <code>variant</code> &#25152;&#20445;&#26377;&#30340;&#21508;&#23454;&#21442;&#35843;&#29992;&#25152;&#25552;&#20379;&#30340;&#20989;&#25968;&#23545;&#35937;<br />
<span class="t-mark">(&#20989;&#25968;&#27169;&#26495;)</span></td>
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