100165713.htm
来自「C#高级编程(第三版),顶死你们。。 。up」· HTM 代码 · 共 161 行
HTM
161 行
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head><title>
28.1.3 接口
</title></head>
<body>
<div class="area">
<div class="col1">
<div class="lineBlue">
</div>
<!-- title -->
<div class="arcTitle">
<h1>
<a href="../16">
C#高级编程（第3版）【全文连载】
</a>
</h1>
<div style="text-align: center; font-size: 15px">
<a href="100165713.htm">
28.1.3 接口
</a>
</div>
<div style="text-align: center; font-size: 15px">
<a class="url" href="../../default.htm">http://book.csdn.net/</a>
2006-10-13 14:41:00
</div>
<div style="margin: 0px auto; width: 700px; border: solid 1px #0b5f98;">
<div style="float: left; width: 16px; background-color: #0b5f98; color: White; padding: 1px;">
图书导读
</div>
<div style="float: right; width: 670px; text-align: left; line-height: 16pt; padding-left: 2px">
<!--导读-->
<h1 id="divCurrentNode" style="color: #b83507; width: 100%; text-align: left; font-size: 12px; padding-left: 2px">当前章节:<a href='100165713.htm'><font color='red'>28.1.3 接口</font></a></h1>
<div id="divRelateNode" style="padding-left: 2px">
<div style='float:left;width:49%'>·<a href='100165710.htm'>28.1 .NET和COM</a></div><div style='float:right;width:49%'>·<a href='100165711.htm'>28.1.1 元数据</a></div><div style='float:left;width:49%'>·<a href='100165712.htm'>28.1.2 释放内存</a></div><div style='float:right;width:49%'>·<a href='100165714.htm'>28.1.4 方法绑定</a></div><div style='float:left;width:49%'>·<a href='100165715.htm'>28.1.5 数据类型</a></div><div style='float:right;width:49%'>·<a href='100165716.htm'>28.1.6 注册</a></div></div>
</div>
</div>
</div>
<!-- main -->
<div id="main">
<div id="text"> <link href="css.css" rel="stylesheet" type="text/css" /><h3 style='margin-top:8.15pt;margin-right:0cm;FTEL:8.15pt;margin-left:
0cm'><span lang=EN-US>28.1.3 </span><span style='font-family:黑体'>接口</span></h3>
<p class=MsoNormal><span style='font-family:宋体'>接口是</span><span lang=EN-US>COM</span><span
style='font-family:宋体'>的核心，它区分了在客户和对象之间使用的契约和实现。接口</span><span lang=EN-US>(</span><span
style='font-family:宋体'>契约</span><span lang=EN-US>)</span><span
style='font-family:宋体'>定义了由组件提供的方法，可以由客户使用。而在</span><span lang=EN-US>.NET</span><span
style='font-family:宋体'>中，接口也有非常重要的作用。</span></p>
<p class=MsoNormal><span lang=EN-US>COM</span><span style='font-family:宋体'>有</span><span
lang=EN-US>3</span><span style='font-family:宋体'>种接口类型：定制接口、分派接口</span><span
lang=EN-US>(dispatch interface)</span><span style='font-family:宋体'>和双重接口。</span></p>
<h4 style='FTEL:21.45pt'><span lang=EN-US>1. </span><span
style='font-family:黑体'>定制接口</span></h4>
<p class=MsoNormal><span style='font-family:宋体'>定制接口派生自接口</span><span
lang=EN-US>IUnknown</span><span style='font-family:宋体'>。定制接口定义了虚拟表</span><span
lang=EN-US>(vtable)</span><span style='font-family:宋体'>中的方法顺序，所以客户可以直接访问接口的方法。这也表示在开发阶段客户需要知道虚拟表，因为方法的绑定是使用内存地址进行的。因此，定制接口不能由脚本客户使用。图</span><span
lang=EN-US>28-1</span><span style='font-family:宋体'>显示了定制接口</span><span
lang=EN-US>IMath</span><span style='font-family:宋体'>的虚拟表，除了接口</span><span
lang=EN-US>IUnknown</span><span style='font-family:宋体'>的方法之外，该接口还提供了方法</span><span
lang=EN-US>Add()</span><span style='font-family:宋体'>和</span><span lang=EN-US>Sub()</span><span
style='font-family:宋体'>。</span></p>
<p align=center style='margin-top:4.9pt'><span lang=EN-US><img width=134 height=106
src="28/image001.jpg"></span></p>
<p class=10><span style='font-family:宋体'>图</span><span lang=EN-US> 28-1</span></p>
<h4 style='FTEL:21.45pt'><span lang=EN-US>2. </span><span
style='font-family:黑体'>分派接口</span></h4>
<p class=MsoNormal><span style='font-family:宋体'>因为脚本客户程序</span><span
lang=EN-US>(</span><span style='font-family:宋体'>和早期的</span><span lang=EN-US>Visual
Basic</span><span style='font-family:宋体'>客户</span><span lang=EN-US>)</span><span
style='font-family:宋体'>不支持定制接口，所以需要另外一种接口类型，而在分派接口中，可用于客户的接口总是</span><span
lang=EN-US>IDispatch</span><span style='font-family:宋体'>接口。</span><span
lang=EN-US>IDispatch</span><span style='font-family:宋体'>接口派生自</span><span
lang=EN-US>IUnknown</span><span style='font-family:宋体'>接口，除了接口</span><span
lang=EN-US>IUnknown</span><span style='font-family:宋体'>的方法之外，它还提供了</span><span
lang=EN-US>4</span><span style='font-family:宋体'>个方法，其中两个比较重要的方法是</span><span
lang=EN-US>GetIDsOfNames()</span><span style='font-family:宋体'>和</span><span
lang=EN-US>Invoke()</span><span style='font-family:宋体'>。如图</span><span
lang=EN-US>28-2</span><span style='font-family:宋体'>所示，在分派接口中需要两个表。第一个表把方法或特性名映射到分派</span><span
lang=EN-US>ID(dispatch id)</span><span style='font-family:宋体'>，第二个表把分派</span><span
lang=EN-US>ID</span><span style='font-family:宋体'>映射到方法或特性的实现。</span></p>
<p class=a><span lang=EN-US><img width=364 height=147
src="28/image002.jpg"></span></p>
<p class=10><span style='font-family:宋体'>图</span><span lang=EN-US> 28-2</span></p>
<p class=MsoNormal><span style='font-family:宋体'>在客户程序调用组件中的方法时，要先调用方法</span><span
lang=EN-US>GetIDsOfNames()</span><span style='font-family:宋体'>，并给它传送要调用的方法名。方法</span><span
lang=EN-US>GetIDsOfNames()</span><span style='font-family:宋体'>会查找名称</span><span
lang=EN-US>-ID</span><span style='font-family:宋体'>表，返回分派</span><span
lang=EN-US>ID</span><span style='font-family:宋体'>，客户程序再使用这个</span><span
lang=EN-US>ID</span><span style='font-family:宋体'>调用方法</span><span lang=EN-US>Invoke()</span><span
style='font-family:宋体'>。</span></p>
<p class=a2 style='margin-top:8.15pt;FTEL:21.45pt'><span
style='font-family:黑体'>注意：</span></p>
<p align=center style='FTEL:8.15pt;FTEL:21.45pt'><span
style='font-family:楷体_GB2312'>通常，</span><span lang=EN-US>IDispatch</span><span
style='font-family:楷体_GB2312'>接口的两个表存储在类型库中，但这不是必须的，一些组件把这两个表存储在其他地方。</span></p>
<h4 style='FTEL:21.45pt'><span lang=EN-US>3. </span><span
style='font-family:黑体'>双重接口</span></h4>
<p class=MsoNormal><span style='font-family:宋体'>可以想像，分派接口比定制接口慢得多。另一方面，脚本客户程序不能使用定制接口。双重接口可以解决这个问题。如图</span><span
lang=EN-US>28-3</span><span style='font-family:宋体'>所示，双重接口派生自</span><span
lang=EN-US>IDispatch</span><span style='font-family:宋体'>接口，但提供了可以在虚拟表中直接使用的接口方法。脚本客户程序可以使用</span><span
lang=EN-US>IDispatch</span><span style='font-family:宋体'>接口调用方法，而了解虚拟表的客户程序可以直接调用方法。</span></p>
<p class=a><span lang=EN-US><img width=364 height=181
src="28/image003.jpg"></span></p>
<p class=10><span style='font-family:宋体'>图</span><span lang=EN-US> 28-3</span></p>
<h4 style='FTEL:21.45pt'><span lang=EN-US>4. </span><span
style='font-family:黑体'>强制类型转换和</span><span lang=EN-US>QueryInterface</span></h4>
<p class=MsoNormal><span style='font-family:宋体'>如果</span><span lang=EN-US>.NET</span><span
style='font-family:宋体'>类实现多个接口，就可以进行强制类型转换，得到一个接口或另一个接口。而在</span><span
lang=EN-US>COM</span><span style='font-family:宋体'>中，接口</span><span lang=EN-US>IUnknown</span><span
style='font-family:宋体'>通过方法</span><span lang=EN-US>QueryInterface()</span><span
style='font-family:宋体'>提供了类似的机制。如上一节所述，接口</span><span lang=EN-US>IUnknown</span><span
style='font-family:宋体'>是其他接口的基础接口，所以可以以任何方式使用方法</span><span lang=EN-US>QueryInterface()</span><span
style='font-family:宋体'>。</span></p>
</div>
<!-- page -->
<div class="page" style="text-align: center">
<a href="100165712.htm">上一页</a> <a href="index.html">首页</a> <a href="100165714.htm">下一页</a>
</div>
<div style="margin: 0px auto; width: 700px; border: solid 1px #0b5f98;">
<div style="float: left; width: 16px; background-color: #0b5f98; color: White; padding: 1px;">
图书导读
</div>
<div style="float: right; width: 670px; text-align: left; line-height: 16pt; padding-left: 2px">
<!--导读-->
<h1 id="divCurrentNode2" style="color: #b83507; width: 100%; text-align: left; font-size: 12px; padding-left: 2px">当前章节:<a href='100165713.htm'><font color='red'>28.1.3 接口</font></a></h1>
<div id="divRealteNod2" style="padding-left: 2px">
<div style='float:left;width:49%'>·<a href='100165710.htm'>28.1 .NET和COM</a></div><div style='float:right;width:49%'>·<a href='100165711.htm'>28.1.1 元数据</a></div><div style='float:left;width:49%'>·<a href='100165712.htm'>28.1.2 释放内存</a></div><div style='float:right;width:49%'>·<a href='100165714.htm'>28.1.4 方法绑定</a></div><div style='float:left;width:49%'>·<a href='100165715.htm'>28.1.5 数据类型</a></div><div style='float:right;width:49%'>·<a href='100165716.htm'>28.1.6 注册</a></div></div>
</div>
</div>
</div>
</div>
</body>
</html>
⌨️ 快捷键说明
复制代码Ctrl + C
搜索代码Ctrl + F
全屏模式F11
增大字号Ctrl + =
减小字号Ctrl + -
显示快捷键?