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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Go by Example 中文版: 数字解析</title>
<link rel=stylesheet href="site.css">
</head>
<script>
onkeydown = (e) => {
if (e.key == "ArrowLeft") {
window.location.href = 'random-numbers';
}
if (e.key == "ArrowRight") {
window.location.href = 'url-parsing';
}
}
</script>
<body>
<div class="example" id="number-parsing">
<h2><a href="./">Go by Example 中文版</a>: 数字解析</h2>
<table>
<tr>
<td class="docs">
<p>从字符串中解析数字在很多程序中是一个基础常见的任务，
而在 Go 中，是这样处理的。</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/WskPmwzIwnT"><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">
<p>内建的 <code>strconv</code> 包提供了数字解析能力。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="kn">import</span> <span class="p">(</span>
<span class="s">"fmt"</span>
<span class="s">"strconv"</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>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>使用 <code>ParseFloat</code>，这里的 <code>64</code> 表示解析的数的位数。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">f</span><span class="p">,</span> <span class="nx">_</span> <span class="o">:=</span> <span class="nx">strconv</span><span class="p">.</span><span class="nf">ParseFloat</span><span class="p">(</span><span class="s">"1.234"</span><span class="p">,</span> <span class="mi">64</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">f</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>在使用 <code>ParseInt</code> 解析整型数时，
例子中的参数 <code>0</code> 表示自动推断字符串所表示的数字的进制。
<code>64</code> 表示返回的整型数是以 64 位存储的。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">i</span><span class="p">,</span> <span class="nx">_</span> <span class="o">:=</span> <span class="nx">strconv</span><span class="p">.</span><span class="nf">ParseInt</span><span class="p">(</span><span class="s">"123"</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="mi">64</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">i</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p><code>ParseInt</code> 会自动识别出字符串是十六进制数。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">d</span><span class="p">,</span> <span class="nx">_</span> <span class="o">:=</span> <span class="nx">strconv</span><span class="p">.</span><span class="nf">ParseInt</span><span class="p">(</span><span class="s">"0x1c8"</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="mi">64</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">d</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p><code>ParseUint</code> 也是可用的。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">u</span><span class="p">,</span> <span class="nx">_</span> <span class="o">:=</span> <span class="nx">strconv</span><span class="p">.</span><span class="nf">ParseUint</span><span class="p">(</span><span class="s">"789"</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="mi">64</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">u</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p><code>Atoi</code> 是一个基础的 10 进制整型数转换函数。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">k</span><span class="p">,</span> <span class="nx">_</span> <span class="o">:=</span> <span class="nx">strconv</span><span class="p">.</span><span class="nf">Atoi</span><span class="p">(</span><span class="s">"135"</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">k</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>在输入错误时，解析函数会返回一个错误。</p>
</td>
<td class="code">
<pre class="chroma">
<span class="nx">_</span><span class="p">,</span> <span class="nx">e</span> <span class="o">:=</span> <span class="nx">strconv</span><span class="p">.</span><span class="nf">Atoi</span><span class="p">(</span><span class="s">"wat"</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">e</span><span class="p">)</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 number-parsing.go
<span class="go">1.234
</span><span class="go">123
</span><span class="go">456
</span><span class="go">789
</span><span class="go">135
</span><span class="go">strconv.ParseInt: parsing "wat": invalid syntax</span></pre>
</td>
</tr>
<tr>
<td class="docs">
<p>下面我们将了解一下另一个常见的解析任务：URL 解析。</p>
</td>
<td class="code empty">
</td>
</tr>
</table>
<p class="next">
下一个例子: <a href="url-parsing.html">URL 解析</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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