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
",__FUNCTION__);
    }
    virtual void doB()
    {
        printf("call %s
",__FUNCTION__);
    }
#if USE_PURE_VIRTUAL_FUNC > 0
    virtual void doC() = 0;//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
");
    }
    virtual void doB()
    {
        printf("child call doB
");
    }
#if USE_PURE_VIRTUAL_FUNC > 0    
    virtual void doC()
    {
        printf("child call doC
");
    }
#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 0;
}