计算机二级C宏–智者的利刃，愚者的恶梦(中)

(续上)例三、用C宏，自动生成代码这方面的例子也是多得很，不过有鉴于很多朋友不用很多编译器，不做嵌入式的开发，我就举个win平台的例子吧。我们知道MFC实现了windows的消息映射，比如：

ON_COMMAND(IDM_ABOUT, OnAbout)

ON_COMMAND(IDM_FILENEW, OnFileNew)

　　它是如何实现的IDM_ABOUT和OnAbout的关联的呢？这要用到几个宏。

#define DECLARE_MESSAGE_MAP() \

private: \

static const AFX_MSGMAP_ENTRY _messageEntries[]; \

protected: \

static AFX_DATA const AFX_MSGMAP messageMap; \

virtual const AFX_MSGMAP* GetMessageMap() const; \

#define BEGIN_MESSAGE_MAP(theClass, baseClass) \

const AFX_MSGMAP* theClass::GetMessageMap() const \

{ return &theClass::messageMap; } \

AFX_COMDAT AFX_DATADEF const AFX_MSGMAP theClass::messageMap = \

{ &baseClass::messageMap, &theClass::_messageEntries[0] }; \

AFX_COMDAT const AFX_MSGMAP_ENTRY theClass::_messageEntries[] = \

{ \

#define ON_COMMAND(id, memberFxn) \

{ WM_COMMAND, 0, (WORD)id, (WORD)id, AfxSig_vv, (AFX_PMSG)memberFxn },

#define END_MESSAGE_MAP() \

{0, 0, 0, 0, AfxSig_end, (AFX_PMSG)0 } \

}; \

#define DECLARE_MESSAGE_MAP() \

private: \

static const AFX_MSGMAP_ENTRY _messageEntries[]; \

protected: \

static AFX_DATA const AFX_MSGMAP messageMap; \

virtual const AFX_MSGMAP* GetMessageMap() const; \

#define BEGIN_MESSAGE_MAP(theClass, baseClass) \

const AFX_MSGMAP* theClass::GetMessageMap() const \

{ return &theClass::messageMap; } \

AFX_COMDAT AFX_DATADEF const AFX_MSGMAP theClass::messageMap = \

{ &baseClass::messageMap, &theClass::_messageEntries[0] }; \
AFX_COMDAT const AFX_MSGMAP_ENTRY theClass::_messageEntries[] = \

{ \

#define ON_COMMAND(id, memberFxn) \

{ WM_COMMAND, 0, (WORD)id, (WORD)id, AfxSig_vv, (AFX_PMSG)memberFxn },

#define END_MESSAGE_MAP() \

{0, 0, 0, 0, AfxSig_end, (AFX_PMSG)0 } \

}; \

　　嘿嘿，就这么几个宏，就构造出一个消息数组来.