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。
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