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panic.html
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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Go by Example 中文版: Panic</title>
<link rel=stylesheet href="site.css">
</head>
<script>
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<body>
<div class="example" id="panic">
<h2><a href="./">Go by Example 中文版</a>: Panic</h2>
<table>
<tr>
<td class="docs">
<p><code>panic</code> 意味着有些出乎意料的错误发生。
通常我们用它来表示程序正常运行中不应该出现的错误，
或者我们不准备优雅处理的错误。</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/EzV2wyI8_qU"><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">"os"</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>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>我们将使用 panic 来检查这个站点上预期之外的错误。
而该站点上只有一个程序：触发 panic。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nb">panic</span><span class="p">(</span><span class="s">"a problem"</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>panic 的一种常见用法是：当函数返回我们不知道如何处理（或不想处理）的错误值时，中止操作。
如果创建新文件时遇到意外错误该如何处理？这里有一个很好的 <code>panic</code> 示例。</p>
</td>
<td class="code">
<pre class="chroma">
<span class="nx">_</span><span class="p">,</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nx">os</span><span class="p">.</span><span class="nf">Create</span><span class="p">(</span><span class="s">"/tmp/file"</span><span class="p">)</span>
<span class="k">if</span> <span class="nx">err</span> <span class="o">!=</span> <span class="kc">nil</span> <span class="p">{</span>
<span class="nb">panic</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span>
<span class="p">}</span>
<span class="p">}</span>
</pre>
</td>
</tr>
</table>
<table>
<tr>
<td class="docs">
<p>运行程序将会导致 panic：
输出一个错误消息和协程追踪信息，并以非零的状态退出程序。</p>
</td>
<td class="code empty leading">
</td>
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<td class="docs">
<p>当 <code>main</code> 中触发第一个 panic 时，程序就会退出而不会执行代码的其余部分。
如果你想看到程序尝试创建 /tmp/file 文件，请注释掉第一个panic。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="gp">$</span> go run panic.go
<span class="go">panic: a problem</span></pre>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<pre class="chroma"><span class="go">goroutine 1 [running]:
</span><span class="go">main.main()
</span><span class="go"> /.../panic.go:12 +0x47
</span><span class="go">...
</span><span class="go">exit status 2</span></pre>
</td>
</tr>
<tr>
<td class="docs">
<p>注意，与某些使用 exception 处理错误的语言不同，
在 Go 中，通常会尽可能的使用返回值来标示错误。</p>
</td>
<td class="code empty">
</td>
</tr>
</table>
<p class="next">
下一个例子: <a href="defer">Defer</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>
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