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<div class="example" id="tickers">
<h2><a href="./">Go by Example</a>: Tickers</h2>
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<p><a href="timers">Timers</a> are for when you want to do
something once in the future - <em>tickers</em> are for when
you want to do something repeatedly at regular
intervals. Here’s an example of a ticker that ticks
periodically until we stop it.</p>
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<a href="http://play.golang.org/p/U0PO7ZZU3l"><img title="Run code" src="play.png" class="run" /></a>
<div class="highlight"><pre><span class="kn">package</span> <span class="nx">main</span>
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<div class="highlight"><pre><span class="kn">import</span> <span class="s">"time"</span>
<span class="kn">import</span> <span class="s">"fmt"</span>
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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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<p>Tickers use a similar mechanism to timers: a
channel that is sent values. Here we’ll use the
<code>range</code> builtin on the channel to iterate over
the values as they arrive every 500ms.</p>
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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="nx">time</span><span class="p">.</span><span class="nx">Millisecond</span> <span class="o">*</span> <span class="mi">500</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="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>
<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>
<span class="p">}</span>
<span class="p">}()</span>
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<p>Tickers can be stopped like timers. Once a ticker
is stopped it won’t receive any more values on its
channel. We’ll stop ours after 1500ms.</p>
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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="nx">time</span><span class="p">.</span><span class="nx">Millisecond</span> <span class="o">*</span> <span class="mi">1500</span><span class="p">)</span>
<span class="nx">ticker</span><span class="p">.</span><span class="nx">Stop</span><span class="p">()</span>
<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>
<span class="p">}</span>
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<p>When we run this program the ticker should tick 3 times
before we stop it.</p>
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<div class="highlight"><pre><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>
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<p class="next">
Next example: <a href="worker-pools">Worker Pools</a>.
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by <a href="https://twitter.com/mmcgrana">@mmcgrana</a> | <a href="mailto:mmcgrana@gmail.com">feedback</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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