133 lines
12 KiB
HTML
133 lines
12 KiB
HTML
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<title>std::mem_fun_ref</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_utility_functional_mem_fun_ref skin-cppreference2 action-view cpp-navbar">
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<div id="content"><a id="top"></a>
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::</span>mem_fun_ref</h1>
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<div id="bodyContent">
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-utility.html">utility</a>‎ | <a href="cpp-utility-functional.html">functional</a></span></div>
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<div>定义于头文件 <code><a href="cpp-header-functional.html"><functional></a></code></div>
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<td></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span> <span class="kw1">class</span> Res, <span class="kw1">class</span> T <span class="sy1">></span><br />
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std<span class="sy4">::</span><span class="me2">mem_fun_ref_t</span><span class="sy1"><</span>Res,T<span class="sy1">></span> mem_fun_ref<span class="br0">(</span> Res <span class="br0">(</span>T<span class="sy4">::</span><span class="sy2">*</span>f<span class="br0">)</span><span class="br0">(</span><span class="br0">)</span> <span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td>(1)</td>
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<td><span class="t-mark">(C++11 中弃用)</span><br />
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<span class="t-mark-rev t-until-cxx17">(C++17 中移除)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span> <span class="kw1">class</span> Res, <span class="kw1">class</span> T <span class="sy1">></span><br />
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std<span class="sy4">::</span><span class="me2">const_mem_fun_ref_t</span><span class="sy1"><</span>Res,T<span class="sy1">></span> mem_fun_ref<span class="br0">(</span> Res <span class="br0">(</span>T<span class="sy4">::</span><span class="sy2">*</span>f<span class="br0">)</span><span class="br0">(</span><span class="br0">)</span> <span class="kw4">const</span> <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td>(1)</td>
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<td><span class="t-mark">(C++11 中弃用)</span><br />
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<span class="t-mark-rev t-until-cxx17">(C++17 中移除)</span></td>
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<tr class="t-dcl t-until-cxx17">
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span> <span class="kw1">class</span> Res, <span class="kw1">class</span> T, <span class="kw1">class</span> Arg <span class="sy1">></span><br />
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std<span class="sy4">::</span><span class="me2">mem_fun1_ref_t</span><span class="sy1"><</span>Res,T,Arg<span class="sy1">></span> mem_fun_ref<span class="br0">(</span> Res <span class="br0">(</span>T<span class="sy4">::</span><span class="sy2">*</span>f<span class="br0">)</span><span class="br0">(</span>Arg<span class="br0">)</span> <span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td>(2)</td>
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<td><span class="t-mark">(C++11 中弃用)</span><br />
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<span class="t-mark-rev t-until-cxx17">(C++17 中移除)</span></td>
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</tr>
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<tr class="t-dcl t-until-cxx17">
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span> <span class="kw1">class</span> Res, <span class="kw1">class</span> T, <span class="kw1">class</span> Arg <span class="sy1">></span><br />
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std<span class="sy4">::</span><span class="me2">const_mem_fun1_ref_t</span><span class="sy1"><</span>Res,T,Arg<span class="sy1">></span> mem_fun_ref<span class="br0">(</span> Res <span class="br0">(</span>T<span class="sy4">::</span><span class="sy2">*</span>f<span class="br0">)</span><span class="br0">(</span>Arg<span class="br0">)</span> <span class="kw4">const</span> <span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td>(2)</td>
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<td><span class="t-mark">(C++11 中弃用)</span><br />
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<span class="t-mark-rev t-until-cxx17">(C++17 中移除)</span></td>
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</tr>
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<tr class="t-dcl-sep">
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<td></td>
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<td></td>
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<p>创建成员函数包装对象，从模板实参推导类型。包装对象期待到 <code>T</code> 类型的引用作为其 <span class="t-c"><span class="mw-geshi cpp source-cpp">operator<span class="br0">(</span><span class="br0">)</span></span></span> 的首个参数。</p>
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<div class="t-li1"><span class="t-li">1)</span> 等效地调用 <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">mem_fun_ref_t</span><span class="sy1"><</span>S,T<span class="sy1">></span><span class="br0">(</span>f<span class="br0">)</span></span></span> 或 <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">const_mem_fun_ref_t</span><span class="sy1"><</span>S,T<span class="sy1">></span><span class="br0">(</span>f<span class="br0">)</span></span></span> 。</div>
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<div class="t-li1"><span class="t-li">2)</span> 等效地调用 <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">mem_fun1_ref_t</span><span class="sy1"><</span>S,T<span class="sy1">></span><span class="br0">(</span>f<span class="br0">)</span></span></span> 或 <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">const_mem_fun1_ref_t</span><span class="sy1"><</span>S,T<span class="sy1">></span><span class="br0">(</span>f<span class="br0">)</span></span></span> 。</div>
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<p>此函数与相关类型于 C++11 弃用并于 C++17 移除，为了让位给更通用的 <span class="t-lc"><a href="cpp-utility-functional-mem_fn.html">std::mem_fn</a></span> 与 <span class="t-lc"><a href="cpp-utility-functional-bind.html">std::bind</a></span> ，它们都从成员函数创建可调用类型的兼容适配器的函数对象。</p>
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<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">参数</span></h3>
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<table class="t-par-begin">
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<td>f</td>
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<td>-</td>
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<td>指向要创建包装的成员函数的指针</td>
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</table>
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<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">返回值</span></h3>
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<p>包装 <code>f</code> 的函数对象。</p>
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<h3><span class="mw-headline" id=".E5.BC.82.E5.B8.B8">异常</span></h3>
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<p>可能抛出实现定义的异常。</p>
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<h3><span class="mw-headline" id=".E6.B3.A8.E8.A7.A3">注解</span></h3>
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<p><span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">mem_fun</span></span></span> 与 <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">mem_fun_ref</span></span></span> 的区别是前者产生的函数包装期待指向对象指针，而后者——期待引用。</p>
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<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">示例</span></h3>
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<div class="t-example">
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<p>用 <code>std::mem_fun_ref</code> 绑定 <span class="t-lc"><a href="cpp-string-basic_string.html">std::string</a></span> 的成员函数 <span class="t-lc"><a href="cpp-string-basic_string-size.html">size()</a></span> 。</p>
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<div class="t-example-live-link"></div>
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<div dir="ltr" class="mw-geshi" style="text-align: left;">
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<div class="cpp source-cpp">
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<pre class="de1"><span class="co2">#include <functional></span>
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<span class="co2">#include <vector></span>
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<span class="co2">#include <string></span>
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<span class="co2">#include <iterator></span>
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<span class="co2">#include <algorithm></span>
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<span class="co2">#include <iostream></span>
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<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
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<span class="br0">{</span>
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<a href="cpp-container-vector.html"><span class="kw1269">std::<span class="me2">vector</span></span></a><span class="sy1"><</span><a href="cpp-string-basic_string.html"><span class="kw1230">std::<span class="me2">string</span></span></a><span class="sy1">></span> v <span class="sy1">=</span> <span class="br0">{</span><span class="st0">"once"</span>, <span class="st0">"upon"</span>, <span class="st0">"a"</span>, <span class="st0">"time"</span><span class="br0">}</span><span class="sy4">;</span>
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<a href="cpp-algorithm-transform.html"><span class="kw1589">std::<span class="me2">transform</span></span></a><span class="br0">(</span>v.<span class="me1">begin</span><span class="br0">(</span><span class="br0">)</span>, v.<span class="me1">end</span><span class="br0">(</span><span class="br0">)</span>,
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<a href="cpp-iterator-ostream_iterator.html"><span class="kw670">std::<span class="me2">ostream_iterator</span></span></a><span class="sy1"><</span><a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a><span class="sy1">></span><span class="br0">(</span><a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a>, <span class="st0">" "</span><span class="br0">)</span>,
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std<span class="sy4">::</span><span class="me2">mem_fun_ref</span><span class="br0">(</span><span class="sy3">&</span>std<span class="sy4">::</span><span class="me2">string</span><span class="sy4">::</span><span class="me2">size</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span></pre></div>
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</div>
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<p>输出：</p>
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<div dir="ltr" class="mw-geshi" style="text-align: left;">
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<div class="text source-text">
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<pre class="de1">4 4 1 4</pre></div>
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</div>
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</div>
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<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">参阅</span></h3>
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<table class="t-dsc-begin">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-utility-functional-mem_fun.html"><span class="t-lines"><span>mem_fun</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-deprecated-cxx11">(C++11 中弃用)</span><span class="t-mark-rev t-until-cxx17">(C++17 中移除)</span></span></span></div>
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</div>
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</td>
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<td>从成员函数指针创建包装器，可以一个对象指针调用<br />
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<span class="t-mark">(函数模板)</span></td>
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</tr>
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</div>
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<div class="visualClear"></div>
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