#include <iostream>

using namespace std;


class Gen0{
    public:
    //只要Gen0的print()是virtual，它的指针指向谁就用谁的print()，
    virtual void print(){
        cout <<"print Gen0"<<endl;
    }
};

class Gen1:public Gen0
{
    public:
        void print(){
            cout <<"print Gen1"<<endl;
        }
};

class Gen2:public Gen1
{
    public:
        void print(){
            cout <<"print Gen2"<<endl;
        }
};

int main(){
    Gen0* p0 = new Gen0();
    Gen1* p1 = new Gen1();
    Gen2* p2 = new Gen2();

    p0->print();
    p1->print();
    p2->print();

    p0 = p1;
    p0->print();

    p0 = p2;
    p0->print();

};

• 输出

print Gen0
print Gen1
print Gen2
print Gen1
print Gen2