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<ol class="chapter"><li class="chapter-item expanded affix "><a href="../index.html">Go语言圣经</a></li><li class="chapter-item expanded affix "><a href="../preface.html">前言</a></li><li class="chapter-item expanded "><a href="../ch1/ch1.html"><strong aria-hidden="true">1.</strong> 入门</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../ch1/ch1-01.html"><strong aria-hidden="true">1.1.</strong> Hello, World</a></li><li class="chapter-item expanded "><a href="../ch1/ch1-02.html"><strong aria-hidden="true">1.2.</strong> 命令行参数</a></li><li class="chapter-item expanded "><a href="../ch1/ch1-03.html"><strong aria-hidden="true">1.3.</strong> 查找重复的行</a></li><li class="chapter-item expanded "><a href="../ch1/ch1-04.html"><strong aria-hidden="true">1.4.</strong> GIF动画</a></li><li class="chapter-item expanded "><a href="../ch1/ch1-05.html"><strong aria-hidden="true">1.5.</strong> 获取URL</a></li><li class="chapter-item expanded "><a href="../ch1/ch1-06.html"><strong aria-hidden="true">1.6.</strong> 并发获取多个URL</a></li><li class="chapter-item expanded "><a href="../ch1/ch1-07.html"><strong aria-hidden="true">1.7.</strong> Web服务</a></li><li class="chapter-item expanded "><a href="../ch1/ch1-08.html"><strong aria-hidden="true">1.8.</strong> 本章要点</a></li></ol></li><li class="chapter-item expanded "><a href="../ch2/ch2.html"><strong aria-hidden="true">2.</strong> 程序结构</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../ch2/ch2-01.html"><strong aria-hidden="true">2.1.</strong> 命名</a></li><li class="chapter-item expanded "><a href="../ch2/ch2-02.html"><strong aria-hidden="true">2.2.</strong> 声明</a></li><li class="chapter-item expanded "><a href="../ch2/ch2-03.html"><strong aria-hidden="true">2.3.</strong> 变量</a></li><li class="chapter-item expanded "><a href="../ch2/ch2-04.html"><strong aria-hidden="true">2.4.</strong> 赋值</a></li><li class="chapter-item expanded "><a href="../ch2/ch2-05.html"><strong aria-hidden="true">2.5.</strong> 类型</a></li><li class="chapter-item expanded "><a href="../ch2/ch2-06.html"><strong aria-hidden="true">2.6.</strong> 包和文件</a></li><li class="chapter-item expanded "><a href="../ch2/ch2-07.html"><strong aria-hidden="true">2.7.</strong> 作用域</a></li></ol></li><li class="chapter-item expanded "><a href="../ch3/ch3.html"><strong aria-hidden="true">3.</strong> 基础数据类型</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../ch3/ch3-01.html"><strong aria-hidden="true">3.1.</strong> 整型</a></li><li class="chapter-item expanded "><a href="../ch3/ch3-02.html"><strong aria-hidden="true">3.2.</strong> 浮点数</a></li><li class="chapter-item expanded "><a href="../ch3/ch3-03.html"><strong aria-hidden="true">3.3.</strong> 复数</a></li><li class="chapter-item expanded "><a href="../ch3/ch3-04.html"><strong aria-hidden="true">3.4.</strong> 布尔型</a></li><li class="chapter-item expanded "><a href="../ch3/ch3-05.html"><strong aria-hidden="true">3.5.</strong> 字符串</a></li><li class="chapter-item expanded "><a href="../ch3/ch3-06.html"><strong aria-hidden="true">3.6.</strong> 常量</a></li></ol></li><li class="chapter-item expanded "><a href="../ch4/ch4.html"><strong aria-hidden="true">4.</strong> 复合数据类型</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../ch4/ch4-01.html"><strong aria-hidden="true">4.1.</strong> 数组</a></li><li class="chapter-item expanded "><a href="../ch4/ch4-02.html"><strong aria-hidden="true">4.2.</strong> Slice</a></li><li class="chapter-item expanded "><a href="../ch4/ch4-03.html"><strong aria-hidden="true">4.3.</strong> Map</a></li><li class="chapter-item expanded "><a href="../ch4/ch4-04.html"><strong aria-hidden="true">4.4.</strong> 结构体</a></li><li class="chapter-item expanded "><a href="../ch4/ch4-05.html"><strong aria-hidden="true">4.5.</strong> JSON</a></li><li class="chapter-item expanded "><a href="../ch4/ch4-06.html"><strong aria-hidd
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<li><em>KusonStack一站式可编程配置技术栈: <a href="https://github.com/KusionStack/kusion">https://github.com/KusionStack/kusion</a></em></li>
<li><em>凹语言™: <a href="https://github.com/wa-lang/wa">https://github.com/wa-lang/wa</a></em></li>
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<h2 id="72-接口类型"><a class="header" href="#72-接口类型">7.2. 接口类型</a></h2>
<p>接口类型具体描述了一系列方法的集合,一个实现了这些方法的具体类型是这个接口类型的实例。</p>
<p>io.Writer类型是用得最广泛的接口之一因为它提供了所有类型的写入bytes的抽象包括文件类型内存缓冲区网络链接HTTP客户端压缩工具哈希等等。io包中定义了很多其它有用的接口类型。Reader可以代表任意可以读取bytes的类型Closer可以是任意可以关闭的值例如一个文件或是网络链接。到现在你可能注意到了很多Go语言中单方法接口的命名习惯</p>
<pre><code class="language-go">package io
type Reader interface {
Read(p []byte) (n int, err error)
}
type Closer interface {
Close() error
}
</code></pre>
<p>再往下看,我们发现有些新的接口类型通过组合已有的接口来定义。下面是两个例子:</p>
<pre><code class="language-go">type ReadWriter interface {
Reader
Writer
}
type ReadWriteCloser interface {
Reader
Writer
Closer
}
</code></pre>
<p>上面用到的语法和结构内嵌相似我们可以用这种方式以一个简写命名一个接口而不用声明它所有的方法。这种方式称为接口内嵌。尽管略失简洁我们可以像下面这样不使用内嵌来声明io.ReadWriter接口。</p>
<pre><code class="language-go">type ReadWriter interface {
Read(p []byte) (n int, err error)
Write(p []byte) (n int, err error)
}
</code></pre>
<p>或者甚至使用一种混合的风格:</p>
<pre><code class="language-go">type ReadWriter interface {
Read(p []byte) (n int, err error)
Writer
}
</code></pre>
<p>上面3种定义方式都是一样的效果。方法顺序的变化也没有影响唯一重要的就是这个集合里面的方法。</p>
<p><strong>练习 7.4</strong> strings.NewReader函数通过读取一个string参数返回一个满足io.Reader接口类型的值和其它值。实现一个简单版本的NewReader用它来构造一个接收字符串输入的HTML解析器§5.2</p>
<p><strong>练习 7.5</strong> io包里面的LimitReader函数接收一个io.Reader接口类型的r和字节数n并且返回另一个从r中读取字节但是当读完n个字节后就表示读到文件结束的Reader。实现这个LimitReader函数</p>
<pre><code class="language-go">func LimitReader(r io.Reader, n int64) io.Reader
</code></pre>
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