C++概念整理

 /*
     面向对象:
             多态,
             继承
             封装
 */
 #include <stdio.h>
 #include <stdlib.h>

 //一旦有了纯虚函数,该对象就不能实例化了.
 #define USE_PURE_VIRTUAL_FUNC 1

 class CBase
 {
 public:
     CBase(){}
     ~CBase(){}
 public:
     void doA()//不标virtual,说明不想被子类重载,如果遇到基类对象指针,则使用该函数时永远是用基类的
     {
         printf("call %s\n",__FUNCTION__);
     }
     virtual void doB()
     {
         printf("call %s\n",__FUNCTION__);
     }
 #if USE_PURE_VIRTUAL_FUNC > 0
     virtual void doC() = ;//父类不实现,但子类必须实现.
 #endif    

 };

 class CChild:public CBase
 {
 public:
     CChild():CBase()
     {};
     ~CChild(){};
 public:
     void doA()
     {
         printf("child call doA\n");
     }
     virtual void doB()
     {
         printf("child call doB\n");
     }
 #if USE_PURE_VIRTUAL_FUNC > 0
     virtual void doC()
     {
         printf("child call doC\n");
     }
 #endif
 };

 int main(void)
 {
 #if USE_PURE_VIRTUAL_FUNC <= 0
     CBase* pB = new CBase();
     CChild* pC = new CChild();

     pB->doA();
     pB->doB();

     pC->doA();
     pC->doB();

     CBase* pTemp = pB;
     pTemp->doA();
     pTemp->doB();

     pTemp = pC;
     pTemp->doA();
     pTemp->doB();

     delete pB;
     delete pC;
 #else
     CChild* pC = new CChild();

     pC->doA();
     pC->doB();

     CBase* pTemp = NULL;
     pTemp = pC;
     pTemp->doA();
     pTemp->doB();
     pTemp->doC();    

     delete pC;
 #endif

     return ;
 }