多态(Polymorphism)和对象切割(Object Slicing)的小例子

如下：

#include  < iostream >
using   namespace  std;
class  Grandfather ... {
public:
    virtual void display()=0;
    void run()...{                    
        cout<<"Grandfather Run!!! ";
    }
} ;
class  Father: public  Grandfather ... {
public:
    int fatherValue;
    void display()...{
        cout<<"Father Display!! ";
    }
    void run()...{
        cout<<"Father Run!!! ";
    }
} ;
class  Uncle: public  Grandfather ... {
public:
    int uncleValue;
    void display()...{
        cout<<"Uncle Display!! ";
    }
    void run()...{
        cout<<"Uncle Run!!! ";
    }
} ;
class  Son: public  Father ... {
public:
    int sonValue;
    void display()...{
        cout<<"Son Display!! ";
    }
} ;
void  main() ... {
    Grandfather* grandfather_pt=NULL;
    Father* father_pt=NULL;
    Son* son_pt=NULL;

    Father father;
    Uncle uncle;
    Son son;

    cout<<"静态绑定 不用virtual关键字： ";
    grandfather_pt=&uncle;
    grandfather_pt->run();
    grandfather_pt=&father;
    grandfather_pt->run();

    cout<<" 动态绑定 纯虚函数： ";
    grandfather_pt=&uncle;
    grandfather_pt->display();
    grandfather_pt=&father;
    grandfather_pt->display();

    cout<<" 指针强制转换 ";
    ( (Father*)(&son) )->display();
//    ( (Father*)(&son) )->run();

    cout<<" 对象强制转换 ";
    ((Father)son).display();        //只允许upcasting，不允许downcasting
    cout<<" 编译器为了防止对象切割的发生，自动调用拷贝构造函数，因此，比较地址： ";
    cout<<( father_pt=&((Father)son) )<<endl;    //注意优先级
    cout<<&son<<endl;
    cout<<"发现二者不同！ ";
}