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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Go by Example မြန်မာဘာသာ: Closing Channels</title>
<link rel=stylesheet href="site.css">
</head>
<script>
onkeydown = (e) => {
if (e.key == "ArrowLeft") {
window.location.href = 'non-blocking-channel-operations';
}
if (e.key == "ArrowRight") {
window.location.href = 'range-over-channels';
}
}
</script>
<body>
<div class="example" id="closing-channels">
<h2><a href="./">Go by Example မြန်မာဘာသာ</a>: Closing Channels</h2>
<table>
<tr>
<td class="docs">
<p>Channel တစ်ခုကို <em>ပိတ်လိုက်ခြင်း (Closing)</em> က အဲဒီ channel ပေါ်မှာ နောက်ထပ်တန်ဖိုးတွေ
ပို့တော့မှာ မဟုတ်ဘူးဆိုတာကို ပြောလိုက်တာပါ။ ဒါက channel ကနေ လက်ခံနေသူတွေဆီကို
ပြီးဆုံးကြောင်း အသိပေးဖို့ အသုံးဝင်ပါတယ်။</p>
</td>
<td class="code empty leading">
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<a href="https://go.dev/play/p/9SQFcddP-Xw"><img title="Run code" src="play.png" class="run" /></a><img title="Copy code" src="clipboard.png" class="copy" />
<pre class="chroma"><span class="kn">package</span> <span class="nx">main</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<pre class="chroma"><span class="kn">import</span> <span class="s">"fmt"</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>ဒီဥပမာမှာ <code>main()</code> goroutine ကနေ worker goroutine ဆီကို
လုပ်ဆောင်ရမယ့် အလုပ်တွေကို ဆက်သွယ်ပေးပို့ဖို့ <code>jobs</code> channel ကို သုံးပါမယ်။
Worker အတွက် နောက်ထပ်အလုပ်မရှိတော့တဲ့အခါ <code>jobs</code> channel ကို <code>close</code> လုပ်ပါမယ်။</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="kd">func</span> <span class="nf">main</span><span class="p">()</span> <span class="p">{</span>
<span class="nx">jobs</span> <span class="o">:=</span> <span class="nb">make</span><span class="p">(</span><span class="kd">chan</span> <span class="kt">int</span><span class="p">,</span> <span class="mi">5</span><span class="p">)</span>
<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>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>ဒါက worker goroutine ပါ။ သူက <code>jobs</code> ကနေ <code>j, more := <-jobs</code> နဲ့
ထပ်ခါထပ်ခါ လက်ခံပါတယ်။ ဒီ special 2-value ပုံစံ လက်ခံမှုမှာ၊ <code>jobs</code> က
<code>close</code> ခံထားရပြီး channel ထဲက တန်ဖိုးအားလုံး လက်ခံပြီးသွားရင်
<code>more</code> တန်ဖိုးက <code>false</code> ဖြစ်သွားပါမယ်။ အလုပ်အားလုံး လုပ်ပြီးသွားတဲ့အခါ
<code>done</code> ပေါ်မှာ အသိပေး (notify) ဖို့ ဒီနည်းကို သုံးပါတယ်။</p>
</td>
<td class="code leading">
<pre class="chroma">
<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="p">{</span>
<span class="nx">j</span><span class="p">,</span> <span class="nx">more</span> <span class="o">:=</span> <span class="o"><-</span><span class="nx">jobs</span>
<span class="k">if</span> <span class="nx">more</span> <span class="p">{</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="s">"received job"</span><span class="p">,</span> <span class="nx">j</span><span class="p">)</span>
<span class="p">}</span> <span class="k">else</span> <span class="p">{</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="s">"received all jobs"</span><span class="p">)</span>
<span class="nx">done</span> <span class="o"><-</span> <span class="kc">true</span>
<span class="k">return</span>
<span class="p">}</span>
<span class="p">}</span>
<span class="p">}()</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>ဒါက worker ဆီကို <code>jobs</code> channel ကနေ အလုပ် 3 ခု ပို့ပြီး
နောက်ဆုံးမှာ channel ကို ပိတ်လိုက်ပါတယ်။</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="k">for</span> <span class="nx">j</span> <span class="o">:=</span> <span class="mi">1</span><span class="p">;</span> <span class="nx">j</span> <span class="o"><=</span> <span class="mi">3</span><span class="p">;</span> <span class="nx">j</span><span class="o">++</span> <span class="p">{</span>
<span class="nx">jobs</span> <span class="o"><-</span> <span class="nx">j</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="s">"sent job"</span><span class="p">,</span> <span class="nx">j</span><span class="p">)</span>
<span class="p">}</span>
<span class="nb">close</span><span class="p">(</span><span class="nx">jobs</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="s">"sent all jobs"</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>အရင်က တွေ့ခဲ့တဲ့ <a href="channel-synchronization">synchronization</a> နည်းလမ်းကို
သုံးပြီး worker ကို စောင့်ပါတယ်။</p>
</td>
<td class="code">
<pre class="chroma">
<span class="o"><-</span><span class="nx">done</span>
<span class="p">}</span>
</pre>
</td>
</tr>
</table>
<table>
<tr>
<td class="docs">
</td>
<td class="code leading">
<pre class="chroma"><span class="gp">$</span> go run closing-channels.go
<span class="go">sent job 1
</span><span class="go">received job 1
</span><span class="go">sent job 2
</span><span class="go">received job 2
</span><span class="go">sent job 3
</span><span class="go">received job 3
</span><span class="go">sent all jobs
</span><span class="go">received all jobs</span></pre>
</td>
</tr>
<tr>
<td class="docs">
<p>Channel တွေကို ပိတ်တဲ့ သဘောတရားက နောက်ဥပမာဖြစ်တဲ့
channel တွေပေါ်မှာ <code>range</code> သုံးတာဆီကို ဦးတည်သွားပါတယ်။</p>
</td>
<td class="code empty">
</td>
</tr>
</table>
<p class="next">
နောက်ဥပမာ: <a href="range-over-channels">Range over Channels</a>.
</p>
<p class="footer">
by <a href="https://markmcgranaghan.com">Mark McGranaghan</a> နှင့် <a href="https://eli.thegreenplace.net">Eli Bendersky</a> | <a href="https://github.com/mmcgrana/gobyexample">source</a> | <a href="https://github.com/mmcgrana/gobyexample#license">license</a>
</p>
</div>
<script>
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codeLines.push('');codeLines.push('package main\u000A');codeLines.push('import \"fmt\"\u000A');codeLines.push('func main() {\u000A jobs :\u003D make(chan int, 5)\u000A done :\u003D make(chan bool)\u000A');codeLines.push(' go func() {\u000A for {\u000A j, more :\u003D \u003C-jobs\u000A if more {\u000A fmt.Println(\"received job\", j)\u000A } else {\u000A fmt.Println(\"received all jobs\")\u000A done \u003C- true\u000A return\u000A }\u000A }\u000A }()\u000A');codeLines.push(' for j :\u003D 1; j \u003C\u003D 3; j++ {\u000A jobs \u003C- j\u000A fmt.Println(\"sent job\", j)\u000A }\u000A close(jobs)\u000A fmt.Println(\"sent all jobs\")\u000A');codeLines.push(' \u003C-done\u000A}\u000A');codeLines.push('');codeLines.push('');
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</body>
</html>