虚函数代码举例

#include <iostream>#include <string>using  namespace std;class  A{public:    virtual void f()    {        cout<<"A"<<endl;    }};class  B:public A{public:    virtual  void  f()    {        cout<<"B"<<endl;    }};int main(){    A *pa=new A();//指向A类的指针    pa->f();    B *pb=(B*)pa;    pb->f();    delete pa,pb;    pa=new B();//指向B类的指针    pa->f();    pb=(B*)pa;    pb->f();    return 0;}

结果为：
A
A
B
B