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closing-channels.html
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closing-channels.html
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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Go by Example 中文版: 通道的关闭</title>
<link rel=stylesheet href="site.css">
</head>
<script>
onkeydown = (e) => {
if (e.key == "ArrowLeft") {
window.location.href = 'non-blocking-channel-operations';
}
if (e.key == "ArrowRight") {
window.location.href = 'range-over-channels';
}
}
</script>
<body>
<div class="example" id="closing-channels">
<h2><a href="./">Go by Example 中文版</a>: 通道的关闭</h2>
<table>
<tr>
<td class="docs">
<p><em>关闭</em> 一个通道意味着不能再向这个通道发送值了。
该特性可以向通道的接收方传达工作已经完成的信息。</p>
</td>
<td class="code empty leading">
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<a href="https://play.studygolang.com/p/abQFh1JyeUl"><img title="Run code" src="play.png" class="run" /></a><img title="Copy code" src="clipboard.png" class="copy" />
<pre class="chroma"><span class="kn">package</span> <span class="nx">main</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<pre class="chroma"><span class="kn">import</span> <span class="s">"fmt"</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>在这个例子中，我们将使用一个 <code>jobs</code> 通道，将工作内容，
从 <code>main()</code> 协程传递到一个工作协程中。
当我们没有更多的任务传递给工作协程时，我们将 <code>close</code> 这个 <code>jobs</code> 通道。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="kd">func</span> <span class="nf">main</span><span class="p">()</span> <span class="p">{</span>
<span class="nx">jobs</span> <span class="o">:=</span> <span class="nb">make</span><span class="p">(</span><span class="kd">chan</span> <span class="kt">int</span><span class="p">,</span> <span class="mi">5</span><span class="p">)</span>
<span class="nx">done</span> <span class="o">:=</span> <span class="nb">make</span><span class="p">(</span><span class="kd">chan</span> <span class="kt">bool</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>这是工作协程。使用 <code>j, more := <- jobs</code> 循环的从 <code>jobs</code> 接收数据。
根据接收的第二个值，如果 <code>jobs</code> 已经关闭了，
并且通道中所有的值都已经接收完毕，那么 <code>more</code> 的值将是 <code>false</code>。
当我们完成所有的任务时，会使用这个特性通过 <code>done</code> 通道通知 main 协程。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="k">go</span> <span class="kd">func</span><span class="p">()</span> <span class="p">{</span>
<span class="k">for</span> <span class="p">{</span>
<span class="nx">j</span><span class="p">,</span> <span class="nx">more</span> <span class="o">:=</span> <span class="o"><-</span><span class="nx">jobs</span>
<span class="k">if</span> <span class="nx">more</span> <span class="p">{</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="s">"received job"</span><span class="p">,</span> <span class="nx">j</span><span class="p">)</span>
<span class="p">}</span> <span class="k">else</span> <span class="p">{</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="s">"received all jobs"</span><span class="p">)</span>
<span class="nx">done</span> <span class="o"><-</span> <span class="kc">true</span>
<span class="k">return</span>
<span class="p">}</span>
<span class="p">}</span>
<span class="p">}()</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>使用 <code>jobs</code> 发送 3 个任务到工作协程中，然后关闭 <code>jobs</code>。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="k">for</span> <span class="nx">j</span> <span class="o">:=</span> <span class="mi">1</span><span class="p">;</span> <span class="nx">j</span> <span class="o"><=</span> <span class="mi">3</span><span class="p">;</span> <span class="nx">j</span><span class="o">++</span> <span class="p">{</span>
<span class="nx">jobs</span> <span class="o"><-</span> <span class="nx">j</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="s">"sent job"</span><span class="p">,</span> <span class="nx">j</span><span class="p">)</span>
<span class="p">}</span>
<span class="nb">close</span><span class="p">(</span><span class="nx">jobs</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="s">"sent all jobs"</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>使用前面学到的<a href="channel-synchronization">通道同步</a>方法等待任务结束。</p>
</td>
<td class="code">
<pre class="chroma">
<span class="o"><-</span><span class="nx">done</span>
<span class="p">}</span>
</pre>
</td>
</tr>
</table>
<table>
<tr>
<td class="docs">
</td>
<td class="code leading">
<pre class="chroma"><span class="gp">$</span> go run closing-channels.go
<span class="go">sent job 1
</span><span class="go">received job 1
</span><span class="go">sent job 2
</span><span class="go">received job 2
</span><span class="go">sent job 3
</span><span class="go">received job 3
</span><span class="go">sent all jobs
</span><span class="go">received all jobs</span></pre>
</td>
</tr>
<tr>
<td class="docs">
<p>根据 <code>关闭通道</code> 的思想，可以引出我们的下一个示例：遍历通道。</p>
</td>
<td class="code empty">
</td>
</tr>
</table>
<p class="next">
下一个例子: <a href="range-over-channels.html">通道遍历</a>
</p>
<p class="footer">
<a href="https://twitter.com/mmcgrana">@mmcgrana</a> 和<a href="https://eli.thegreenplace.net">Eli Bendersky</a>编写 | <a href="https://github.com/gobyexample-cn">gobyexample-cn</a> 翻译 | <a href="https://github.com/gobyexample-cn/gobyexample/issues">反馈</a> | <a href="https://github.com/gobyexample-cn/gobyexample">源码</a> | <a href="https://github.com/mmcgrana/gobyexample#license">license</a> </p>
</p>
</div>
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