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pointers.html
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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Go by Example 中文版: 指针</title>
<link rel=stylesheet href="site.css">
</head>
<script>
onkeydown = (e) => {
if (e.key == "ArrowLeft") {
window.location.href = 'recursion';
}
if (e.key == "ArrowRight") {
window.location.href = 'strings-and-runes';
}
}
</script>
<body>
<div class="example" id="pointers">
<h2><a href="./">Go by Example 中文版</a>: 指针</h2>
<table>
<tr>
<td class="docs">
<p>Go 支持 <em><a href="http://zh.wikipedia.org/wiki/%E6%8C%87%E6%A8%99_(%E9%9B%BB%E8%85%A6%E7%A7%91%E5%AD%B8)">指针</a></em>，
允许在程序中通过 <code>引用传递</code> 来传递值和数据结构。</p>
</td>
<td class="code empty leading">
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<a href="https://play.studygolang.com/p/deS4CF9BzRP"><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>我们将通过两个函数：<code>zeroval</code> 和 <code>zeroptr</code> 来比较 <code>指针</code> 和 <code>值</code>。
<code>zeroval</code> 有一个 <code>int</code> 型参数，所以使用值传递。
<code>zeroval</code> 将从调用它的那个函数中得到一个实参的拷贝：ival。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="kd">func</span> <span class="nf">zeroval</span><span class="p">(</span><span class="nx">ival</span> <span class="kt">int</span><span class="p">)</span> <span class="p">{</span>
<span class="nx">ival</span> <span class="p">=</span> <span class="mi">0</span>
<span class="p">}</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p><code>zeroptr</code> 有一个和上面不同的参数：<code>*int</code>，这意味着它使用了 <code>int</code> 指针。
紧接着，函数体内的 <code>*iptr</code> 会 <em>解引用</em> 这个指针，从它的内存地址得到这个地址当前对应的值。
对解引用的指针赋值，会改变这个指针引用的真实地址的值。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="kd">func</span> <span class="nf">zeroptr</span><span class="p">(</span><span class="nx">iptr</span> <span class="o">*</span><span class="kt">int</span><span class="p">)</span> <span class="p">{</span>
<span class="o">*</span><span class="nx">iptr</span> <span class="p">=</span> <span class="mi">0</span>
<span class="p">}</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
</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">i</span> <span class="o">:=</span> <span class="mi">1</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="s">"initial:"</span><span class="p">,</span> <span class="nx">i</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<pre class="chroma"> <span class="nf">zeroval</span><span class="p">(</span><span class="nx">i</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">"zeroval:"</span><span class="p">,</span> <span class="nx">i</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>通过 <code>&i</code> 语法来取得 <code>i</code> 的内存地址，即指向 <code>i</code> 的指针。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nf">zeroptr</span><span class="p">(</span><span class="o">&</span><span class="nx">i</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">"zeroptr:"</span><span class="p">,</span> <span class="nx">i</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>指针也是可以被打印的。</p>
</td>
<td class="code">
<pre class="chroma">
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="s">"pointer:"</span><span class="p">,</span> <span class="o">&</span><span class="nx">i</span><span class="p">)</span>
<span class="p">}</span>
</pre>
</td>
</tr>
</table>
<table>
<tr>
<td class="docs">
<p><code>zeroval</code> 在 <code>main</code> 函数中不能改变 <code>i</code> 的值，
但是 <code>zeroptr</code> 可以，因为它有这个变量的内存地址的引用。</p>
</td>
<td class="code">
<pre class="chroma">
<span class="gp">$</span> go run pointers.go
<span class="go">initial: 1
</span><span class="go">zeroval: 1
</span><span class="go">zeroptr: 0
</span><span class="go">pointer: 0x42131100</span></pre>
</td>
</tr>
</table>
<p class="next">
下一个例子: <a href="strings-and-runes">字符串和rune类型</a>
</p>
<p class="footer">
<a href="https://twitter.com/mmcgrana">@mmcgrana</a> 和<a href="https://eli.thegreenplace.net">Eli Bendersky</a>编写 | <a href="https://github.com/gobyexample-cn">gobyexample-cn</a> 翻译 | <a href="https://github.com/gobyexample-cn/gobyexample/issues">反馈</a> | <a href="https://github.com/gobyexample-cn/gobyexample">源码</a> | <a href="https://github.com/mmcgrana/gobyexample#license">license</a> </p>
</p>
</div>
<script>
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</body>
</html>