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timers.html
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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Go by Example 中文版: Timer</title>
<link rel=stylesheet href="site.css">
</head>
<script>
onkeydown = (e) => {
if (e.key == "ArrowLeft") {
window.location.href = 'range-over-channels';
}
if (e.key == "ArrowRight") {
window.location.href = 'tickers';
}
}
</script>
<body>
<div class="example" id="timers">
<h2><a href="./">Go by Example 中文版</a>: Timer</h2>
<table>
<tr>
<td class="docs">
<p>我们经常需要在未来的某个时间点运行 Go 代码，或者每隔一定时间重复运行代码。
Go 内置的 <em>定时器</em> 和 <em>打点器</em> 特性让这些变得很简单。
我们会先学习定时器，然后再学习<a href="tickers">打点器</a>。</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/9Ho_6IS5JtL"><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>定时器表示在未来某一时刻的独立事件。
你告诉定时器需要等待的时间，然后它将提供一个用于通知的通道。
这里的定时器将等待 2 秒。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">timer1</span> <span class="o">:=</span> <span class="nx">time</span><span class="p">.</span><span class="nf">NewTimer</span><span class="p">(</span><span class="mi">2</span> <span class="o">*</span> <span class="nx">time</span><span class="p">.</span><span class="nx">Second</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p><code><-timer1.C</code> 会一直阻塞，
直到定时器的通道 <code>C</code> 明确的发送了定时器失效的值。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="o"><-</span><span class="nx">timer1</span><span class="p">.</span><span class="nx">C</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="s">"Timer 1 fired"</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>如果你需要的仅仅是单纯的等待，使用 <code>time.Sleep</code> 就够了。
使用定时器的原因之一就是，你可以在定时器触发之前将其取消。
例如这样。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">timer2</span> <span class="o">:=</span> <span class="nx">time</span><span class="p">.</span><span class="nf">NewTimer</span><span class="p">(</span><span class="nx">time</span><span class="p">.</span><span class="nx">Second</span><span class="p">)</span>
<span class="k">go</span> <span class="kd">func</span><span class="p">()</span> <span class="p">{</span>
<span class="o"><-</span><span class="nx">timer2</span><span class="p">.</span><span class="nx">C</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="s">"Timer 2 fired"</span><span class="p">)</span>
<span class="p">}()</span>
<span class="nx">stop2</span> <span class="o">:=</span> <span class="nx">timer2</span><span class="p">.</span><span class="nf">Stop</span><span class="p">()</span>
<span class="k">if</span> <span class="nx">stop2</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">"Timer 2 stopped"</span><span class="p">)</span>
<span class="p">}</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>给 <code>timer2</code> 足够的时间来触发它，以证明它实际上已经停止了。</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">2</span> <span class="o">*</span> <span class="nx">time</span><span class="p">.</span><span class="nx">Second</span><span class="p">)</span>
<span class="p">}</span>
</pre>
</td>
</tr>
</table>
<table>
<tr>
<td class="docs">
<p>第一个定时器将在程序开始后大约 2s 触发，
但是第二个定时器还未触发就停止了。</p>
</td>
<td class="code">
<pre class="chroma">
<span class="gp">$</span> go run timers.go
<span class="go">Timer 1 fired
</span><span class="go">Timer 2 stopped</span></pre>
</td>
</tr>
</table>
<p class="next">
下一个例子: <a href="tickers.html">Ticker</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(' timer1 :\u003D time.NewTimer(2 * time.Second)\u000A');codeLines.push(' \u003C-timer1.C\u000A fmt.Println(\"Timer 1 fired\")\u000A');codeLines.push(' timer2 :\u003D time.NewTimer(time.Second)\u000A go func() {\u000A \u003C-timer2.C\u000A fmt.Println(\"Timer 2 fired\")\u000A }()\u000A stop2 :\u003D timer2.Stop()\u000A if stop2 {\u000A fmt.Println(\"Timer 2 stopped\")\u000A }\u000A');codeLines.push(' time.Sleep(2 * time.Second)\u000A}\u000A');codeLines.push('');
</script>
<script src="site.js" async></script>
</body>
</html>