157 lines
5.7 KiB
Plaintext
157 lines
5.7 KiB
Plaintext
<!DOCTYPE html>
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<meta charset="utf-8">
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<title>Go by Example: Channels</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="channels">
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<h2><a href="./">Go by Example</a>: Channels</h2>
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<table>
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<tr>
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<td class="docs">
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<p><em>Channels</em> are the pipes that connect concurrent
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goroutines. You can send values into channels from one
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goroutine and receive those values into another
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goroutine.</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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<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/bRGMAqinovA"><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 class="docs">
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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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<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>Create a new channel with <code>make(chan val-type)</code>.
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Channels are typed by the values they convey.</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">messages</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>
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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><em>Send</em> a value into a channel using the <code>channel <-</code>
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syntax. Here we send <code>"ping"</code> to the <code>messages</code>
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channel we made above, from a new goroutine.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="k">go</span> <span class="kd">func</span><span class="p">()</span> <span class="p">{</span> <span class="nx">messages</span> <span class="o"><-</span> <span class="s">"ping"</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>The <code><-channel</code> syntax <em>receives</em> a value from the
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channel. Here we’ll receive the <code>"ping"</code> message
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we sent above and print it out.</p>
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</td>
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<td class="code">
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<div class="highlight"><pre> <span class="nx">msg</span> <span class="o">:=</span> <span class="o"><-</span><span class="nx">messages</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">msg</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 the program the <code>"ping"</code> message is
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successfully passed from one goroutine to another via
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our 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="gp">$</span> go run channels.go
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<span class="go">ping</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>By default sends and receives block until both the
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sender and receiver are ready. This property allowed
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us to wait at the end of our program for the <code>"ping"</code>
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message without having to use any other synchronization.</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="channel-buffering">Channel Buffering</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/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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</body>
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</html>
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