模拟虚函数机制

komany

1. // Base.h: interface for the Base class.
   
2. //
   
3. //////////////////////////////////////////////////////////////////////
   
4. #if !defined(AFX_BASE_H__BC0F931E_FB88_46BB_AACF_81A971F3B966__INCLUDED_)
   
5. #define AFX_BASE_H__BC0F931E_FB88_46BB_AACF_81A971F3B966__INCLUDED_
   
6. #if _MSC_VER > 1000
   
7. #pragma once
   
8. #endif // _MSC_VER > 1000
   
9. #include <iOStream.h>
   
10. #include <memory.h>
    
11. class Base;
    
12. typedef void (Base::*FUNC_TYPE1)();
    
13. class Base  
    
14. {
    
15. public:
    
16.     static FUNC_TYPE1 m_VTable[];
    
17.     FUNC_TYPE1       *m_lpVTable;
    
18. public:
    
19.     Base();
    
20.     ~Base();
    
21. public:
    
22.     void vsSayHello()
    
23.     {
    
24.         cout << "BASE::SAYHELLO" << endl;
    
25.     }
    
26.     void vsSayGoodBye()
    
27.     {
    
28.          cout << "BASE::SAYGOODBYE" << endl;
    
29.     }
    
30.    
    
31. };
    
32. 
    
33. #endif // !defined(AFX_BASE_H__BC0F931E_FB88_46BB_AACF_81A971F3B966__INCLUDED_)
    

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1. // Base.cpp: implementation of the Base class.
   
2. //
   
3. //////////////////////////////////////////////////////////////////////
   
4. #include "stdafx.h"
   
5. #include "Base.h"
   
6. //////////////////////////////////////////////////////////////////////
   
7. // Construction/Destruction
   
8. //////////////////////////////////////////////////////////////////////
   
9. FUNC_TYPE1 Base::m_VTable[] = {
   
10.     Base::vsSayHello,
    
11.     Base::vsSayGoodBye
    
12. };
    
13. Base::Base()
    
14. {
    
15.     m_lpVTable = Base::m_VTable;
    
16. }
    
17. Base:: ~Base()
    
18. {
    
19.    
    
20. }

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1. // Derive.h: interface for the Derive class.
   
2. //
   
3. //////////////////////////////////////////////////////////////////////
   
4. #if !defined(AFX_DERIVE_H__FB413D6B_2A11_40FB_9B58_E32FEF4FA050__INCLUDED_)
   
5. #define AFX_DERIVE_H__FB413D6B_2A11_40FB_9B58_E32FEF4FA050__INCLUDED_
   
6. #if _MSC_VER > 1000
   
7. #pragma once
   
8. #endif // _MSC_VER > 1000
   
9. #include "Base.h"
   
10. class Derive;
    
11. typedef void (Derive::*FUNC_TYPE2)();
    
12. class Derive : public Base  
    
13. {
    
14. public:
    
15.     static FUNC_TYPE2 m_VTable[];
    
16. public:
    
17.     Derive();
    
18.     ~Derive();
    
19. public:
    
20.     void vsSayHello()
    
21.     {
    
22.         cout << "Derive::SAYHELLO" << endl;
    
23.     }
    
24.     void vsSayGoodBye()
    
25.     {
    
26.         cout << "Derive::SAYGOODBYE" << endl;
    
27.     }
    
28.    
    
29. };
    
30. 
    
31. #endif // !defined(AFX_DERIVE_H__FB413D6B_2A11_40FB_9B58_E32FEF4FA050__INCLUDED_)
    

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1. // Derive.cpp: implementation of the Derive class.
   
2. //
   
3. //////////////////////////////////////////////////////////////////////
   
4. #include "stdafx.h"
   
5. #include "Derive.h"
   
6. //////////////////////////////////////////////////////////////////////
   
7. // Construction/Destruction
   
8. //////////////////////////////////////////////////////////////////////
   
9. FUNC_TYPE2 Derive::m_VTable[] = {
   
10.     Derive::vsSayHello,
    
11.     Derive::vsSayGoodBye
    
12. };
    
13. Derive::Derive()
    
14. {
    
15.     memcpy(Derive::m_VTable, m_lpVTable, 4);
    
16.     m_VTable[0] = Derive::vsSayHello;
    
17.     m_VTable[1] = Derive::vsSayGoodBye;
    
18.     m_lpVTable = (FUNC_TYPE1 *)Derive::m_VTable;   
    
19. }
    
20. Derive:: ~Derive()
    
21. {
    
22.    
    
23. }

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1. // 模拟虚函数机制.cpp : Defines the entry point for the console application.
   
2. //
   
3. #include "stdafx.h"
   
4. #include "Derive.h"
   
5. void CallFunction(Base* lpBase)
   
6. {
   
7.     (lpBase->*(lpBase->m_lpVTable[0]))();
   
8.     (lpBase->*(lpBase->m_lpVTable[1]))();
   
9. }
   
10. int main(int argc, char* argv[])
    
11. {
    
12.     Base theBase;
    
13.     Derive theDerive;
    
14.     CallFunction(&theBase);
    
15.     CallFunction(&theDerive);
    
16.     return 0;
    
17. }
    

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oldman

/:002 不会c，看不懂……