161 lines
9.8 KiB
HTML
161 lines
9.8 KiB
HTML
<!DOCTYPE html>
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<html lang="zh" dir="ltr" class="client-nojs" xmlns="http://www.w3.org/1999/xhtml" xml:lang="zh">
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<title>std::is_error_code_enum<std::io_errc></title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_io_io_errc_is_error_code_enum skin-cppreference2 action-view cpp-navbar">
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<div id="cpp-content-base">
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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>is_error_code_enum<small><std::io_errc></small></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-io.html">io</a>‎ | <a href="cpp-io-io_errc.html">io errc</a></span></div>
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<div id="mw-content-text" lang="zh" dir="ltr" class="mw-content-ltr" xml:lang="zh">
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<div>定义于头文件 <code><a href="cpp-header-ios.html"><ios></a></code></div>
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<td></td>
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<td></td>
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<tr class="t-dcl t-since-cxx11">
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span> <span class="sy1">></span><br />
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<span class="kw1">struct</span> is_error_code_enum<span class="sy1"><</span><a href="cpp-io-io_errc.html"><span class="kw1810">std::<span class="me2">io_errc</span></span></a><span class="sy1">></span> <span class="sy4">:</span> <span class="kw1">public</span> <a href="cpp-types-integral_constant.html"><span class="kw649">std::<span class="me2">true_type</span></span></a> <span class="br0">{</span> <span class="br0">}</span><span class="sy4">;</span></span></div>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx11">(C++11 起)</span></td>
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<td></td>
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<td></td>
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<td></td>
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<p>此 <span class="t-lc"><a href="cpp-error-error_code-is_error_code_enum.html">std::is_error_code_enum</a></span> 特化指示其他库组件 <span class="t-lc"><a href="cpp-io-io_errc.html">std::io_errc</a></span> 的值是保有错误码的枚举，这使得它们可以隐式转换到并赋值给 <span class="t-lc"><a href="cpp-error-error_code.html">std::error_code</a></span> 类型的对象。</p>
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<div class="t-inherited">
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<h2><span class="mw-headline" id=".E7.BB.A7.E6.89.BF.E8.87.AA_std::integral_constant">继承自 <a href="cpp-types-integral_constant.html"><span style="font-size:0.7em; line-height:130%">std::</span>integral_constant</a></span></h2>
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<h3><span class="mw-headline" id=".E6.88.90.E5.91.98.E5.B8.B8.E9.87.8F">成员常量</span></h3>
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<table class="t-dsc-begin">
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<div><span class="t-lines"><span>value</span></span></div>
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<div><span class="t-lines"><span><span class="t-cmark">[静态]</span></span></span></div>
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</td>
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<td><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">true</span></span></span><br />
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<span class="t-mark">(公开静态成员常量)</span></td>
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</table>
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<h3><span class="mw-headline" id=".E6.88.90.E5.91.98.E5.87.BD.E6.95.B0">成员函数</span></h3>
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<div class="t-dsc-member-div">
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<div><span class="t-lines"><span>operator bool</span></span></div>
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</td>
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<td>转换对象为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">bool</span></span></span> ，返回 <code>value</code><br />
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<span class="t-mark">(公开成员函数)</span></td>
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<div><span class="t-lines"><span>operator()</span></span></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx14">(C++14)</span></span></span></div>
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</td>
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<td>返回 <code>value</code><br />
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<span class="t-mark">(公开成员函数)</span></td>
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</tr>
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</table>
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<h3><span class="mw-headline" id=".E6.88.90.E5.91.98.E7.B1.BB.E5.9E.8B">成员类型</span></h3>
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<table class="t-dsc-begin">
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<td>类型</td>
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<td>定义</td>
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<td><code>value_type</code></td>
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<td><code>bool</code></td>
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<td><code>type</code></td>
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<td><span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-types-integral_constant.html"><span class="kw647">std::<span class="me2">integral_constant</span></span></a><span class="sy1"><</span><span class="kw4">bool</span>, value<span class="sy1">></span></span></span></td>
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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><span class="t-c"><span class="mw-geshi cpp source-cpp">e.<span class="me1">code</span><span class="br0">(</span><span class="br0">)</span></span></span> 与 <span class="t-lc"><a href="cpp-io-io_errc.html">std::io_errc::stream</a></span> 的比较能编译，因为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-error-error_code-is_error_code_enum.html"><span class="kw878">std::<span class="me2">is_error_code_enum</span></span></a><span class="sy1"><</span><a href="cpp-io-io_errc.html"><span class="kw1810">std::<span class="me2">io_errc</span></span></a><span class="sy1">></span><span class="sy4">::</span><span class="me2">value</span> <span class="sy1">==</span> <span class="kw2">true</span></span></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 <iostream></span>
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<span class="co2">#include <fstream></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-io-basic_ifstream.html"><span class="kw1732">std::<span class="me2">ifstream</span></span></a> f<span class="br0">(</span><span class="st0">"doesn't exist"</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="kw1">try</span> <span class="br0">{</span>
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f.<span class="me1">exceptions</span><span class="br0">(</span>f.<span class="me1">failbit</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span> <span class="kw1">catch</span> <span class="br0">(</span><span class="kw4">const</span> <a href="cpp-io-ios_base-failure.html"><span class="kw1670">std::<span class="me2">ios_base</span><span class="sy4">::</span><span class="me2">failure</span></span></a><span class="sy3">&</span> e<span class="br0">)</span> <span class="br0">{</span>
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<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"Caught an ios_base::failure.<span class="es1">\n</span>"</span><span class="sy4">;</span>
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<span class="kw1">if</span><span class="br0">(</span>e.<span class="me1">code</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1">==</span> <a href="cpp-io-io_errc.html"><span class="kw1811">std::<span class="me2">io_errc</span><span class="sy4">::</span><span class="me2">stream</span></span></a><span class="br0">)</span>
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<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"The error code is std::io_errc::stream<span class="es1">\n</span>"</span><span class="sy4">;</span>
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<span class="br0">}</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">Caught an ios_base::failure.
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The error code is std::io_errc::stream</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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<div class="t-dsc-member-div">
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<div><a href="cpp-error-error_code-is_error_code_enum.html"><span class="t-lines"><span>is_error_code_enum</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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</div>
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</td>
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<td>鉴别类是否可作为 error_code 枚举<br />
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<span class="t-mark">(类模板)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-error-error_code.html"><span class="t-lines"><span>error_code</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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</div>
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</td>
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<td>保有依赖于平台的错误码<br />
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<span class="t-mark">(类)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-io-io_errc.html"><span class="t-lines"><span>io_errc</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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</div>
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</td>
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<td>IO 流的错误码<br />
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<span class="t-mark">(枚举)</span></td>
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</tr>
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</table>
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</div>
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<div class="visualClear"></div>
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</div>
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</div>
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</body>
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