klarkxy/hustoj
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity
Files
master
hustoj/web/cppreference-zh/chmhelp/cpp-utility-functional-ref.html
klarkxy 196e706fe4 上传cppreference
2025-08-01 12:57:54 +08:00

249 lines
18 KiB
HTML
Raw Permalink Blame History

<!DOCTYPE html>
<html lang="zh" dir="ltr" class="client-nojs" xmlns="http://www.w3.org/1999/xhtml" xml:lang="zh">
<head><meta http-equiv="x-ua-compatible" content="ie=edge">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>std::ref, std::cref</title>
<link rel="stylesheet" href="ext.css" />
<link rel="stylesheet" href="site_modules.css" />
</head>
<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_utility_functional_ref skin-cppreference2 action-view cpp-navbar">
<div id="cpp-content-base">
<div id="content"><a id="top"></a>
<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::</span>ref, <span style="font-size:0.7em; line-height:130%">std::</span>cref</h1>
<div id="bodyContent">
<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-functional.html">functional</a></span></div>
<div id="mw-content-text" lang="zh" dir="ltr" class="mw-content-ltr" xml:lang="zh">
<table class="t-dcl-begin">
<tbody>
<tr class="t-dsc-header">
<td>
<div>&#23450;&#20041;&#20110;&#22836;&#25991;&#20214; <code><a href="cpp-header-functional.html">&lt;functional&gt;</a></code></div>
</td>
<td></td>
<td></td>
</tr>
</tbody>
<tbody class="t-dcl-rev t-dcl-rev-num">
<tr class="t-dcl-rev-aux">
<td></td>
<td rowspan="142">(1)</td>
<td></td>
</tr>
<tr class="t-dcl t-since-cxx11 t-until-cxx20">
<td>
<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="sy1">&gt;</span><br />
<a href="cpp-utility-functional-reference_wrapper.html"><span class="kw1068">std::<span class="me2">reference_wrapper</span></span></a><span class="sy1">&lt;</span>T<span class="sy1">&gt;</span> ref<span class="br0">(</span> T<span class="sy3">&amp;</span> t <span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span></span></div>
</td>
<td class="t-dcl-nopad"></td>
<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span><br />
<span class="t-mark-rev t-until-cxx20">(C++20 &#21069;)</span></td>
</tr>
<tr class="t-dcl t-since-cxx20">
<td>
<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="sy1">&gt;</span><br />
<span class="kw4">constexpr</span> <a href="cpp-utility-functional-reference_wrapper.html"><span class="kw1068">std::<span class="me2">reference_wrapper</span></span></a><span class="sy1">&lt;</span>T<span class="sy1">&gt;</span> ref<span class="br0">(</span> T<span class="sy3">&amp;</span> t <span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span></span></div>
</td>
<td class="t-dcl-nopad"></td>
<td><span class="t-mark-rev t-since-cxx20">(C++20 &#36215;)</span></td>
</tr>
</tbody>
<tbody></tbody>
<tbody class="t-dcl-rev t-dcl-rev-num">
<tr class="t-dcl-rev-aux">
<td></td>
<td rowspan="142">(2)</td>
<td></td>
</tr>
<tr class="t-dcl t-since-cxx11 t-until-cxx20">
<td>
<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="sy1">&gt;</span><br /></span>
<p><a href="cpp-utility-functional-reference_wrapper.html"><span class="kw1068">std::<span class="me2">reference_wrapper</span></span></a><span class="sy1">&lt;</span>T<span class="sy1">&gt;</span><br /></p>
&nbsp; &nbsp; ref<span class="br0">(</span> <a href="cpp-utility-functional-reference_wrapper.html"><span class="kw1068">std::<span class="me2">reference_wrapper</span></span></a><span class="sy1">&lt;</span>T<span class="sy1">&gt;</span> t <span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span></div>
</td>
<td class="t-dcl-nopad"></td>
<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span><br />
<span class="t-mark-rev t-until-cxx20">(C++20 &#21069;)</span></td>
</tr>
<tr class="t-dcl t-since-cxx20">
<td>
<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="sy1">&gt;</span><br /></span>
<p><span class="kw4">constexpr</span> <a href="cpp-utility-functional-reference_wrapper.html"><span class="kw1068">std::<span class="me2">reference_wrapper</span></span></a><span class="sy1">&lt;</span>T<span class="sy1">&gt;</span><br /></p>
&nbsp; &nbsp; ref<span class="br0">(</span> <a href="cpp-utility-functional-reference_wrapper.html"><span class="kw1068">std::<span class="me2">reference_wrapper</span></span></a><span class="sy1">&lt;</span>T<span class="sy1">&gt;</span> t <span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span></div>
</td>
<td class="t-dcl-nopad"></td>
<td><span class="t-mark-rev t-since-cxx20">(C++20 &#36215;)</span></td>
</tr>
</tbody>
<tbody>
<tr class="t-dcl t-since-cxx11">
<td>
<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="sy1">&gt;</span><br />
<span class="kw4">void</span> ref<span class="br0">(</span> <span class="kw4">const</span> T<span class="sy3">&amp;&amp;</span> <span class="br0">)</span> <span class="sy1">=</span> delete<span class="sy4">;</span></span></div>
</td>
<td>(3)</td>
<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span></td>
</tr>
</tbody>
<tbody class="t-dcl-rev t-dcl-rev-num">
<tr class="t-dcl-rev-aux">
<td></td>
<td rowspan="142">(4)</td>
<td></td>
</tr>
<tr class="t-dcl t-since-cxx11 t-until-cxx20">
<td>
<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="sy1">&gt;</span><br />
<a href="cpp-utility-functional-reference_wrapper.html"><span class="kw1068">std::<span class="me2">reference_wrapper</span></span></a><span class="sy1">&lt;</span><span class="kw4">const</span> T<span class="sy1">&gt;</span> cref<span class="br0">(</span> <span class="kw4">const</span> T<span class="sy3">&amp;</span> t <span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span></span></div>
</td>
<td class="t-dcl-nopad"></td>
<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span><br />
<span class="t-mark-rev t-until-cxx20">(C++20 &#21069;)</span></td>
</tr>
<tr class="t-dcl t-since-cxx20">
<td>
<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="sy1">&gt;</span><br />
<span class="kw4">constexpr</span> <a href="cpp-utility-functional-reference_wrapper.html"><span class="kw1068">std::<span class="me2">reference_wrapper</span></span></a><span class="sy1">&lt;</span><span class="kw4">const</span> T<span class="sy1">&gt;</span> cref<span class="br0">(</span> <span class="kw4">const</span> T<span class="sy3">&amp;</span> t <span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span></span></div>
</td>
<td class="t-dcl-nopad"></td>
<td><span class="t-mark-rev t-since-cxx20">(C++20 &#36215;)</span></td>
</tr>
</tbody>
<tbody></tbody>
<tbody class="t-dcl-rev t-dcl-rev-num">
<tr class="t-dcl-rev-aux">
<td></td>
<td rowspan="142">(5)</td>
<td></td>
</tr>
<tr class="t-dcl t-since-cxx11 t-until-cxx20">
<td>
<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="sy1">&gt;</span><br /></span>
<p><a href="cpp-utility-functional-reference_wrapper.html"><span class="kw1068">std::<span class="me2">reference_wrapper</span></span></a><span class="sy1">&lt;</span><span class="kw4">const</span> T<span class="sy1">&gt;</span><br /></p>
&nbsp; &nbsp; cref<span class="br0">(</span> <a href="cpp-utility-functional-reference_wrapper.html"><span class="kw1068">std::<span class="me2">reference_wrapper</span></span></a><span class="sy1">&lt;</span>T<span class="sy1">&gt;</span> t <span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span></div>
</td>
<td class="t-dcl-nopad"></td>
<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span><br />
<span class="t-mark-rev t-until-cxx20">(C++20 &#21069;)</span></td>
</tr>
<tr class="t-dcl t-since-cxx20">
<td>
<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="sy1">&gt;</span><br /></span>
<p><span class="kw4">constexpr</span> <a href="cpp-utility-functional-reference_wrapper.html"><span class="kw1068">std::<span class="me2">reference_wrapper</span></span></a><span class="sy1">&lt;</span><span class="kw4">const</span> T<span class="sy1">&gt;</span><br /></p>
&nbsp; &nbsp; cref<span class="br0">(</span> <a href="cpp-utility-functional-reference_wrapper.html"><span class="kw1068">std::<span class="me2">reference_wrapper</span></span></a><span class="sy1">&lt;</span>T<span class="sy1">&gt;</span> t <span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span></div>
</td>
<td class="t-dcl-nopad"></td>
<td><span class="t-mark-rev t-since-cxx20">(C++20 &#36215;)</span></td>
</tr>
</tbody>
<tbody>
<tr class="t-dcl t-since-cxx11">
<td>
<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="sy1">&gt;</span><br />
<span class="kw4">void</span> cref<span class="br0">(</span> <span class="kw4">const</span> T<span class="sy3">&amp;&amp;</span> <span class="br0">)</span> <span class="sy1">=</span> delete<span class="sy4">;</span></span></div>
</td>
<td>(6)</td>
<td><span class="t-mark-rev t-since-cxx11">(C++11 &#36215;)</span></td>
</tr>
<tr class="t-dcl-sep">
<td></td>
<td></td>
<td></td>
</tr>
</tbody>
</table>
<p>&#20989;&#25968;&#27169;&#26495; <code>ref</code> &#19982; <code>cref</code> &#26159;&#29983;&#25104; <span class="t-lc"><a href="cpp-utility-functional-reference_wrapper.html">std::reference_wrapper</a></span> &#31867;&#22411;&#23545;&#35937;&#30340;&#24110;&#21161;&#20989;&#25968;&#65292;&#23427;&#20204;&#29992;<a href="cpp-language-template_argument_deduction.html">&#27169;&#26495;&#23454;&#21442;&#25512;&#23548;</a>&#30830;&#23450;&#32467;&#26524;&#30340;&#27169;&#26495;&#23454;&#21442;&#12290;</p>
<table class="t-rev-begin">
<tr class="t-rev t-since-cxx20">
<td>
<p><code>T</code> &#21487;&#20026;&#19981;&#23436;&#25972;&#31867;&#22411;&#12290;</p>
</td>
<td><span class="t-mark-rev t-since-cxx20">(C++20 &#36215;)</span></td>
</tr>
</table>
<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">&#21442;&#25968;</span></h3>
<table class="t-par-begin">
<tr class="t-par">
<td>t</td>
<td>-</td>
<td>&#38656;&#35201;&#34987;&#21253;&#35013;&#30340;&#21040;&#23545;&#35937;&#30340;&#24038;&#20540;&#24341;&#29992;&#65292;&#25110; <span class="t-lc"><a href="cpp-utility-functional-reference_wrapper.html">std::reference_wrapper</a></span> &#30340;&#23454;&#20363;</td>
</tr>
</table>
<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">&#36820;&#22238;&#20540;</span></h3>
<div class="t-li1"><span class="t-li">1)</span> <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-utility-functional-reference_wrapper.html"><span class="kw1068">std::<span class="me2">reference_wrapper</span></span></a><span class="sy1">&lt;</span>T<span class="sy1">&gt;</span><span class="br0">(</span>t<span class="br0">)</span></span></span></div>
<div class="t-li1"><span class="t-li">2)</span> <span class="t-c"><span class="mw-geshi cpp source-cpp">t</span></span></div>
<div class="t-li1"><span class="t-li">4)</span> <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-utility-functional-reference_wrapper.html"><span class="kw1068">std::<span class="me2">reference_wrapper</span></span></a><span class="sy1">&lt;</span><span class="kw4">const</span> T<span class="sy1">&gt;</span><span class="br0">(</span>t<span class="br0">)</span></span></span></div>
<div class="t-li1"><span class="t-li">5)</span> <span class="t-c"><span class="mw-geshi cpp source-cpp">t</span></span></div>
<div class="t-li1"><span class="t-li">3,6)</span> &#21491;&#20540;&#24341;&#29992;&#21253;&#35013;&#22120;&#34987;&#21024;&#38500;&#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>
<div dir="ltr" class="mw-geshi" style="text-align: left;">
<div class="cpp source-cpp">
<pre class="de1"><span class="co2">#include &lt;functional&gt;</span>
<span class="co2">#include &lt;iostream&gt;</span>
<span class="kw4">void</span> f<span class="br0">(</span><span class="kw4">int</span><span class="sy3">&amp;</span> n1, <span class="kw4">int</span><span class="sy3">&amp;</span> n2, <span class="kw4">const</span> <span class="kw4">int</span><span class="sy3">&amp;</span> n3<span class="br0">)</span>
<span class="br0">{</span>
<a href="cpp-io-cout.html"><span class="kw1756">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">&quot;In function: &quot;</span> <span class="sy1">&lt;&lt;</span> n1 <span class="sy1">&lt;&lt;</span> <span class="st0">&#39; &#39;</span> <span class="sy1">&lt;&lt;</span> n2 <span class="sy1">&lt;&lt;</span> <span class="st0">&#39; &#39;</span> <span class="sy1">&lt;&lt;</span> n3 <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span><span class="sy4">;</span>
<span class="sy2">++</span>n1<span class="sy4">;</span> <span class="co1">// &#22686;&#21152;&#23384;&#20648;&#20110;&#20989;&#25968;&#23545;&#35937;&#30340; n1 &#21103;&#26412;</span>
<span class="sy2">++</span>n2<span class="sy4">;</span> <span class="co1">// &#22686;&#21152; main() &#30340; n2</span>
<span class="co1">// ++n3; // &#32534;&#35793;&#38169;&#35823;</span>
<span class="br0">}</span>
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
<span class="br0">{</span>
<span class="kw4">int</span> n1 <span class="sy1">=</span> <span class="nu0">1</span>, n2 <span class="sy1">=</span> <span class="nu0">2</span>, n3 <span class="sy1">=</span> <span class="nu0">3</span><span class="sy4">;</span>
<a href="cpp-utility-functional-function.html"><span class="kw1059">std::<span class="me2">function</span></span></a><span class="sy1">&lt;</span><span class="kw4">void</span><span class="br0">(</span><span class="br0">)</span><span class="sy1">&gt;</span> bound_f <span class="sy1">=</span> <a href="cpp-utility-functional-bind.html"><span class="kw1052">std::<span class="me2">bind</span></span></a><span class="br0">(</span>f, n1, std<span class="sy4">::</span><span class="me2">ref</span><span class="br0">(</span>n2<span class="br0">)</span>, std<span class="sy4">::</span><span class="me2">cref</span><span class="br0">(</span>n3<span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
n1 <span class="sy1">=</span> <span class="nu0">10</span><span class="sy4">;</span>
n2 <span class="sy1">=</span> <span class="nu0">11</span><span class="sy4">;</span>
n3 <span class="sy1">=</span> <span class="nu0">12</span><span class="sy4">;</span>
<a href="cpp-io-cout.html"><span class="kw1756">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">&quot;Before function: &quot;</span> <span class="sy1">&lt;&lt;</span> n1 <span class="sy1">&lt;&lt;</span> <span class="st0">&#39; &#39;</span> <span class="sy1">&lt;&lt;</span> n2 <span class="sy1">&lt;&lt;</span> <span class="st0">&#39; &#39;</span> <span class="sy1">&lt;&lt;</span> n3 <span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span><span class="sy4">;</span>
bound_f<span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
<a href="cpp-io-cout.html"><span class="kw1756">std::<span class="me2">cout</span></span></a> <span class="sy1">&lt;&lt;</span> <span class="st0">&quot;After function: &quot;</span> <span class="sy1">&lt;&lt;</span> n1 <span class="sy1">&lt;&lt;</span> <span class="st0">&#39; &#39;</span> <span class="sy1">&lt;&lt;</span> n2 <span class="sy1">&lt;&lt;</span> <span class="st0">&#39; &#39;</span> <span class="sy1">&lt;&lt;</span> n3 <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></pre></div>
</div>
<p>&#36755;&#20986;&#65306;</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;">
<div class="text source-text">
<pre class="de1">Before function: 10 11 12
In function: 1 11 12
After function: 10 12 12</pre></div>
</div>
</div>
<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>
<table class="dsctable" style="font-size:0.8em">
<tr>
<th>DR</th>
<th>&#24212;&#29992;&#20110;</th>
<th>&#20986;&#29256;&#26102;&#30340;&#34892;&#20026;</th>
<th>&#27491;&#30830;&#34892;&#20026;</th>
</tr>
<tr>
<td><a rel="nofollow" class="external text" href="https://cplusplus.github.io/LWG/issue3146">LWG 3146</a></td>
<td>C++11</td>
<td>&#35299;&#21253;&#35013;&#37325;&#36733;&#26377;&#26102;&#23548;&#33268;&#38169;&#35823;</td>
<td>&#20351;&#20043;&#22987;&#32456;&#21512;&#27861;</td>
</tr>
</table>
<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">&#21442;&#38405;</span></h3>
<table class="t-dsc-begin">
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><a href="cpp-utility-functional-reference_wrapper.html"><span class="t-lines"><span>reference_wrapper</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
</div>
</td>
<td><a href="cpp-named_req-CopyConstructible.html"><span style="font-style:italic">&#21487;&#22797;&#21046;&#26500;&#36896;</span> <span style="font-family: Georgia, &#39;DejaVu Serif&#39;, serif; font-style:italic">(CopyConstructible)</span></a> &#19988;<a href="cpp-named_req-CopyAssignable.html"><span style="font-style:italic">&#21487;&#22797;&#21046;&#36171;&#20540;</span> <span style="font-family: Georgia, &#39;DejaVu Serif&#39;, serif; font-style:italic">(CopyAssignable)</span></a> &#30340;&#24341;&#29992;&#21253;&#35013;&#22120;<br />
<span class="t-mark">(&#31867;&#27169;&#26495;)</span></td>
</tr>
</table>
</div>
<div class="visualClear"></div>
</div>
</div>
</div>
</body>
</html>
Reference in New Issue View Git Blame Copy Permalink