www.pudn.com > vcppnet.rar > dyncreat.cpp

#include  
 
#define RUNTIME_CLASS(class_name) (&class_name::class##class_name) 
 
class CObject; 
 
struct CRuntimeClass 
{ 
    char m_lpszClassName[21]; 
    int m_nObjectSize; 
    CObject* (*m_pfnCreateObject)(); 
    CObject* CreateObject(); 
}; 
 
// not a true abstract class because there are no pure  
//  virtual functions, but user can't create CObject objects  
//  because of the protected constructor 
class CObject 
{ 
public: 
    // not pure because derived classes don't necessarily 
    // implement it 
    virtual CRuntimeClass* GetRuntimeClass() const { return NULL; } 
         
    // We never construct objects of class CObject, but in MFC we 
    //  use this to get class hierarchy information 
    static CRuntimeClass classCObject;        // DYNAMIC 
     virtual ~CObject() {};  // gotta have it 
protected: 
    CObject() { printf("CObject constructor\n"); } 
}; 
 
CRuntimeClass CObject::classCObject = { "CObject",  
    sizeof(CObject), NULL }; 
 
CObject* CRuntimeClass::CreateObject() 
{ 
    return (*m_pfnCreateObject)(); // indirect function call 
} 
 
class CAlpha : public CObject 
{ 
public: 
    virtual CRuntimeClass* GetRuntimeClass()  
        const { return &classCAlpha; } 
    static CRuntimeClass classCAlpha;        // DYNAMIC 
    static CObject* CreateObject();          // DYNCREATE 
protected: 
    CAlpha() { printf("CAlpha constructor\n"); } 
}; 
 
CRuntimeClass CAlpha::classCAlpha = { "CAlpha",  
    sizeof(CAlpha), CAlpha::CreateObject }; 
 
CObject* CAlpha::CreateObject() // static function 
{ 
    return new CAlpha;     
} 
 
class CBeta : public CObject 
{ 
public: 
    virtual CRuntimeClass* GetRuntimeClass()  
        const { return &classCBeta; } 
    static CRuntimeClass classCBeta;         // DYNAMIC 
    static CObject* CreateObject();          // DYNCREATE 
protected: 
    CBeta() { printf("CBeta constructor\n"); } 
}; 
 
CRuntimeClass CBeta::classCBeta = { "CBeta",  
    sizeof(CBeta), CBeta::CreateObject }; 
 
CObject* CBeta::CreateObject() // static function 
{ 
    return new CBeta;     
} 
 
int main() 
{ 
    printf("Entering dyncreate main\n"); 
 
    CRuntimeClass* pRTCAlpha = RUNTIME_CLASS(CAlpha); 
    CObject* pObj1 = pRTCAlpha->CreateObject(); 
    printf("class of pObj1 = %s\n",  
        pObj1->GetRuntimeClass()->m_lpszClassName); 
 
    CRuntimeClass* pRTCBeta = RUNTIME_CLASS(CBeta); 
    CObject* pObj2 = pRTCBeta->CreateObject(); 
    printf("class of pObj2 = %s\n",  
        pObj2->GetRuntimeClass()->m_lpszClassName); 
 
    delete pObj1; 
    delete pObj2; 
    return 0; 
}