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tickers.html
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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Go by Example 中文版: Ticker</title>
<link rel=stylesheet href="site.css">
</head>
<script>
onkeydown = (e) => {
if (e.key == "ArrowLeft") {
window.location.href = 'timers';
}
if (e.key == "ArrowRight") {
window.location.href = 'worker-pools';
}
}
</script>
<body>
<div class="example" id="tickers">
<h2><a href="./">Go by Example 中文版</a>: Ticker</h2>
<table>
<tr>
<td class="docs">
<p><a href="timers">定时器</a> 是当你想要在未来某一刻执行一次时使用的
- <em>打点器</em> 则是为你想要以固定的时间间隔重复执行而准备的。
这里是一个打点器的例子，它将定时的执行，直到我们将它停止。</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/db3-n6hSCyW"><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="p">(</span>
<span class="s">"fmt"</span>
<span class="s">"time"</span>
<span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
</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>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>打点器和定时器的机制有点相似：使用一个通道来发送数据。
这里我们使用通道内建的 <code>select</code>，等待每 500ms 到达一次的值。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">ticker</span> <span class="o">:=</span> <span class="nx">time</span><span class="p">.</span><span class="nf">NewTicker</span><span class="p">(</span><span class="mi">500</span> <span class="o">*</span> <span class="nx">time</span><span class="p">.</span><span class="nx">Millisecond</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">
</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="k">select</span> <span class="p">{</span>
<span class="k">case</span> <span class="o"><-</span><span class="nx">done</span><span class="p">:</span>
<span class="k">return</span>
<span class="k">case</span> <span class="nx">t</span> <span class="o">:=</span> <span class="o"><-</span><span class="nx">ticker</span><span class="p">.</span><span class="nx">C</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">"Tick at"</span><span class="p">,</span> <span class="nx">t</span><span class="p">)</span>
<span class="p">}</span>
<span class="p">}</span>
<span class="p">}()</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>打点器可以和定时器一样被停止。
打点器一旦停止，将不能再从它的通道中接收到值。
我们将在运行 1600ms 后停止这个打点器。</p>
</td>
<td class="code">
<pre class="chroma">
<span class="nx">time</span><span class="p">.</span><span class="nf">Sleep</span><span class="p">(</span><span class="mi">1600</span> <span class="o">*</span> <span class="nx">time</span><span class="p">.</span><span class="nx">Millisecond</span><span class="p">)</span>
<span class="nx">ticker</span><span class="p">.</span><span class="nf">Stop</span><span class="p">()</span>
<span class="nx">done</span> <span class="o"><-</span> <span class="kc">true</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="s">"Ticker stopped"</span><span class="p">)</span>
<span class="p">}</span>
</pre>
</td>
</tr>
</table>
<table>
<tr>
<td class="docs">
<p>当我们运行这个程序时，打点器会在我们停止它前打点 3 次。</p>
</td>
<td class="code">
<pre class="chroma">
<span class="gp">$</span> go run tickers.go
<span class="go">Tick at 2012-09-23 11:29:56.487625 -0700 PDT
</span><span class="go">Tick at 2012-09-23 11:29:56.988063 -0700 PDT
</span><span class="go">Tick at 2012-09-23 11:29:57.488076 -0700 PDT
</span><span class="go">Ticker stopped</span></pre>
</td>
</tr>
</table>
<p class="next">
下一个例子: <a href="worker-pools">工作池</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>
<script>
var codeLines = [];
codeLines.push('');codeLines.push('package main\u000A');codeLines.push('import (\u000A \"fmt\"\u000A \"time\"\u000A)\u000A');codeLines.push('func main() {\u000A');codeLines.push(' ticker :\u003D time.NewTicker(500 * time.Millisecond)\u000A done :\u003D make(chan bool)\u000A');codeLines.push(' go func() {\u000A for {\u000A select {\u000A case \u003C-done:\u000A return\u000A case t :\u003D \u003C-ticker.C:\u000A fmt.Println(\"Tick at\", t)\u000A }\u000A }\u000A }()\u000A');codeLines.push(' time.Sleep(1600 * time.Millisecond)\u000A ticker.Stop()\u000A done \u003C- true\u000A fmt.Println(\"Ticker stopped\")\u000A}\u000A');codeLines.push('');
</script>
<script src="site.js" async></script>
</body>
</html>