public/structs

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      <h2><a href="./">Go by Example မြန်မာဘာသာ</a>: Structs</h2>
      
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            <p>Go ရဲ့ <em>structs</em> ဆိုတာက type မတူတဲ့ values တွေကို ပေါင်းစည်းတဲ့နေရာမှာသုံးတယ်။
အထူးသဖြင့် ကိုယ်ပိုင် data type တွေဖန်တီးတဲ့အချိန်မှာအသုံးပြုကြတယ်။</p>

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            <a href="https://go.dev/play/p/6k9hwvIrqvd"><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>
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          <pre class="chroma"><span class="kn">import</span> <span class="s">&#34;fmt&#34;</span>
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            <p>ဒီမှာဆို <code>person</code> struct type ထဲမှာ <code>name</code> နှင့် age ဆိုတဲ့ field တွေရှိတယ်။</p>

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<span class="kd">type</span> <span class="nx">person</span> <span class="kd">struct</span> <span class="p">{</span>
    <span class="nx">name</span> <span class="kt">string</span>
    <span class="nx">age</span>  <span class="kt">int</span>
<span class="p">}</span>
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            <p>ဒီ <code>newPerson</code> function မှာဆိုရင် name ပေးပီးတော့ person struct တခုတည်ဆောက်လိုက်တယ်။</p>

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<span class="kd">func</span> <span class="nf">newPerson</span><span class="p">(</span><span class="nx">name</span> <span class="kt">string</span><span class="p">)</span> <span class="o">*</span><span class="nx">person</span> <span class="p">{</span>
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            <p>local variable ဖြစ်လို့ pointer ကို စိတ်ချလက်ချ return ပေးလို့ရတယ်။
local variable က ပျောက်မသွားဘူး။</p>

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    <span class="nx">p</span> <span class="o">:=</span> <span class="nx">person</span><span class="p">{</span><span class="nx">name</span><span class="p">:</span> <span class="nx">name</span><span class="p">}</span>
    <span class="nx">p</span><span class="p">.</span><span class="nx">age</span> <span class="p">=</span> <span class="mi">42</span>
    <span class="k">return</span> <span class="o">&amp;</span><span class="nx">p</span>
<span class="p">}</span>
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          <pre class="chroma"><span class="kd">func</span> <span class="nf">main</span><span class="p">()</span> <span class="p">{</span>
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            <p>ဒီ syntax က struct အသစ်တခုတည်ဆောက်လိုက်တယ်။</p>

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    <span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">person</span><span class="p">{</span><span class="s">&#34;Bob&#34;</span><span class="p">,</span> <span class="mi">20</span><span class="p">})</span>
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            <p>struct ကို initialize လုပ်နေတဲ့အချိန်မှာ name fields တွေကိုသတ်မှတ်ပေးလို့ရတယ်။</p>

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    <span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">person</span><span class="p">{</span><span class="nx">name</span><span class="p">:</span> <span class="s">&#34;Alice&#34;</span><span class="p">,</span> <span class="nx">age</span><span class="p">:</span> <span class="mi">30</span><span class="p">})</span>
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            <p>age ကိုမသတ်မှတ်ထားဘူးဆို zero default ဖြစ်သွားမယ်။</p>

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    <span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">person</span><span class="p">{</span><span class="nx">name</span><span class="p">:</span> <span class="s">&#34;Fred&#34;</span><span class="p">})</span>
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            <p>ဒီနေရာမှာ <code>&amp;</code> prefix ကိုသုံးထားတာက person data ရဲ့ address ကိုပေးထားတာ။
data ကိုပေးထားတာမဟုတ်ဘူး။ struct ရဲ့ pointer ပေါ့။</p>

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    <span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="o">&amp;</span><span class="nx">person</span><span class="p">{</span><span class="nx">name</span><span class="p">:</span> <span class="s">&#34;Ann&#34;</span><span class="p">,</span> <span class="nx">age</span><span class="p">:</span> <span class="mi">40</span><span class="p">})</span>
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            <p>Go မှာ person struct တခုတည်ဆောက်တော့မယ်ဆိုရင် constructor function
တခ ုတည်ဆောက်ပီးသုံးရမယ် တိုက်ရိုက်မသုံးရဘူးဆိုပီးလက်ခံထားကြတယ်။</p>

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    <span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nf">newPerson</span><span class="p">(</span><span class="s">&#34;Jon&#34;</span><span class="p">))</span>
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            <p>struct fields တွေကို access လုပ်မယ်ဆို dot နဲ့လုပ်တယ်။</p>

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    <span class="nx">s</span> <span class="o">:=</span> <span class="nx">person</span><span class="p">{</span><span class="nx">name</span><span class="p">:</span> <span class="s">&#34;Sean&#34;</span><span class="p">,</span> <span class="nx">age</span><span class="p">:</span> <span class="mi">50</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="nx">s</span><span class="p">.</span><span class="nx">name</span><span class="p">)</span>
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            <p>struct pointer တွေသုံးမယ်ဆိုလဲ dot ကိုသုံးလို့ရတယ်။
pointer တွေရဲကနေ data ကိုယူတာကို GO ကနောက်ကွယ်ကနေလုပ်ပေးလိမ့်မယ်။</p>

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    <span class="nx">sp</span> <span class="o">:=</span> <span class="o">&amp;</span><span class="nx">s</span>
    <span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">sp</span><span class="p">.</span><span class="nx">age</span><span class="p">)</span>
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            <p>Structs တွေက mutable (ပြောင်းလဲနိုင်တယ်)</p>

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    <span class="nx">sp</span><span class="p">.</span><span class="nx">age</span> <span class="p">=</span> <span class="mi">51</span>
    <span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">sp</span><span class="p">.</span><span class="nx">age</span><span class="p">)</span>
<span class="p">}</span>
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          <pre class="chroma"><span class="gp">$</span> go run structs.go
<span class="go">{Bob 20}
</span><span class="go">{Alice 30}
</span><span class="go">{Fred 0}
</span><span class="go">&amp;{Ann 40}
</span><span class="go">&amp;{Jon 42}
</span><span class="go">Sean
</span><span class="go">50
</span><span class="go">51</span></pre>
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        နောက်ဥပမာ: <a href="methods">Methods</a>.
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      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>
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