140 lines
6.0 KiB
Plaintext
140 lines
6.0 KiB
Plaintext
<!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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<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/Rgc_UDvHv6a"><img title="Run code" class="run" src="data:image/png;base64,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" /></a>
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<div class="highlight"><pre><span class="kn">package</span> <span class="nx">main</span>
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</pre></div>
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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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<div class="highlight"><pre><span class="kn">import</span> <span class="s">"time"</span>
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<span class="kn">import</span> <span class="s">"fmt"</span>
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</pre></div>
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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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<div class="highlight"><pre><span class="kd">func</span> <span class="nx">main</span><span class="p">()</span> <span class="p">{</span>
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</pre></div>
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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>range</code> builtin on the channel to iterate over
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the values as they arrive every 500ms.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="nx">ticker</span> <span class="o">:=</span> <span class="nx">time</span><span class="p">.</span><span class="nx">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="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="nx">t</span> <span class="o">:=</span> <span class="k">range</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="nx">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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</pre></div>
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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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<div class="highlight"><pre> <span class="nx">time</span><span class="p">.</span><span class="nx">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="nx">Stop</span><span class="p">()</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">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></div>
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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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<div class="highlight"><pre><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</span>
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<span class="go">Tick at 2012-09-23 11:29:56.988063 -0700 PDT</span>
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<span class="go">Tick at 2012-09-23 11:29:57.488076 -0700 PDT</span>
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<span class="go">Ticker stopped</span>
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</pre></div>
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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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</body>
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</html>
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