174 lines
6.9 KiB
Plaintext
Generated
174 lines
6.9 KiB
Plaintext
Generated
<!DOCTYPE html>
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<html>
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<head>
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<meta charset="utf-8">
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<title>Go by Example: Tickers</title>
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<link rel=stylesheet href="site.css">
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</head>
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<script>
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onkeydown = (e) => {
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if (e.key == "ArrowLeft") {
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window.location.href = 'timers';
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}
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if (e.key == "ArrowRight") {
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window.location.href = 'worker-pools';
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}
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}
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</script>
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<body>
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<div class="example" id="tickers">
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<h2><a href="./">Go by Example</a>: Tickers</h2>
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<table>
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<tr>
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<td class="docs">
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<p><a href="timers">Timers</a> are for when you want to do
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something once in the future - <em>tickers</em> are for when
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you want to do something repeatedly at regular
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intervals. Here’s an example of a ticker that ticks
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periodically until we stop it.</p>
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</td>
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<td class="code empty leading">
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</td>
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</tr>
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<tr>
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<td class="docs">
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</td>
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<td class="code leading">
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<a href="http://play.golang.org/p/gs6zoJP-Pl9"><img title="Run code" src="play.png" class="run" /></a><img title="Copy code" src="clipboard.png" class="copy" />
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<pre class="chroma"><span class="kn">package</span> <span class="nx">main</span>
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</pre>
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</td>
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</tr>
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<tr>
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<td class="docs">
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</td>
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<td class="code leading">
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<pre class="chroma"><span class="kn">import</span> <span class="p">(</span>
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<span class="s">"fmt"</span>
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<span class="s">"time"</span>
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<span class="p">)</span>
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</pre>
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</td>
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</tr>
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<tr>
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<td class="docs">
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</td>
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<td class="code leading">
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<pre class="chroma"><span class="kd">func</span> <span class="nf">main</span><span class="p">()</span> <span class="p">{</span>
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</pre>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>Tickers use a similar mechanism to timers: a
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channel that is sent values. Here we’ll use the
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<code>select</code> builtin on the channel to await the
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values as they arrive every 500ms.</p>
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</td>
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<td class="code leading">
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<pre class="chroma">
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<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>
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<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>
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</pre>
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</td>
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</tr>
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<tr>
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<td class="docs">
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</td>
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<td class="code leading">
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<pre class="chroma"> <span class="k">go</span> <span class="kd">func</span><span class="p">()</span> <span class="p">{</span>
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<span class="k">for</span> <span class="p">{</span>
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<span class="k">select</span> <span class="p">{</span>
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<span class="k">case</span> <span class="o"><-</span><span class="nx">done</span><span class="p">:</span>
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<span class="k">return</span>
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<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>
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<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>
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<span class="p">}</span>
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<span class="p">}</span>
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<span class="p">}()</span>
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</pre>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>Tickers can be stopped like timers. Once a ticker
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is stopped it won’t receive any more values on its
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channel. We’ll stop ours after 1600ms.</p>
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</td>
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<td class="code">
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<pre class="chroma">
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<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>
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<span class="nx">ticker</span><span class="p">.</span><span class="nf">Stop</span><span class="p">()</span>
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<span class="nx">done</span> <span class="o"><-</span> <span class="kc">true</span>
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<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>
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<span class="p">}</span>
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</pre>
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</td>
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</tr>
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</table>
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<table>
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<tr>
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<td class="docs">
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<p>When we run this program the ticker should tick 3 times
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before we stop it.</p>
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</td>
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<td class="code">
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<pre class="chroma">
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<span class="gp">$</span> go run tickers.go
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<span class="go">Tick at 2012-09-23 11:29:56.487625 -0700 PDT
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</span><span class="go">Tick at 2012-09-23 11:29:56.988063 -0700 PDT
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</span><span class="go">Tick at 2012-09-23 11:29:57.488076 -0700 PDT
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</span><span class="go">Ticker stopped</span></pre>
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</td>
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</tr>
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</table>
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<p class="next">
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Next example: <a href="worker-pools">Worker Pools</a>.
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</p>
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<p class="footer">
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by <a href="https://markmcgranaghan.com">Mark McGranaghan</a> | <a href="https://github.com/mmcgrana/gobyexample/blob/master/examples/tickers">source</a> | <a href="https://github.com/mmcgrana/gobyexample#license">license</a>
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</p>
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</div>
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<script>
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var codeLines = [];
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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('');
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</script>
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<script src="site.js" async></script>
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</body>
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</html>
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