156 lines
5.1 KiB
Plaintext
156 lines
5.1 KiB
Plaintext
<!DOCTYPE html>
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<html>
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<head>
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<meta http-eqiv="content-type" content="text/html;charset=utf-8">
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<title>Go by Example: Range over Channels</title>
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<div class="example" id="range-over-channels">
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<h2><a href="./">Go by Example</a>: Range over Channels</h2>
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<table>
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<tr>
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<td class="docs">
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<p>In a <a href="range">previous</a> example we saw how <code>for</code> and
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<code>range</code> provide iteration over basic data structures.
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We can also use this syntax to iterate over
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values received from a channel.</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/WN7NNh9tvh"><img title="Run code" src="play.png" class="run" /></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">"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>We’ll iterate over 2 values in the <code>queue</code> channel.</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">queue</span> <span class="o">:=</span> <span class="nb">make</span><span class="p">(</span><span class="kd">chan</span> <span class="kt">string</span><span class="p">,</span> <span class="mi">2</span><span class="p">)</span>
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<span class="nx">queue</span> <span class="o"><-</span> <span class="s">"one"</span>
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<span class="nx">queue</span> <span class="o"><-</span> <span class="s">"two"</span>
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<span class="nb">close</span><span class="p">(</span><span class="nx">queue</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>This <code>range</code> iterates over each element as it’s
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received from <code>queue</code>. Because we <code>close</code>d the
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channel above, the iteration terminates after
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receiving the 2 elements. If we didn’t <code>close</code> it
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we’d block on a 3rd receive in the loop.</p>
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</td>
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<td class="code">
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<div class="highlight"><pre> <span class="k">for</span> <span class="nx">elem</span> <span class="o">:=</span> <span class="k">range</span> <span class="nx">queue</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="nx">elem</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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</table>
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<table>
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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="gp">$</span> go run range-over-channels.go
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<span class="go">one</span>
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<span class="go">two</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>This example also showed that it’s possible to close
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a non-empty channel but still have the remaining
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values be received.</p>
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</td>
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<td class="code empty">
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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="timers">Timers</a>.
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</p>
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<p class="footer">
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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/range-over-channels">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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