c++ 虚方法

#include <iostream>
#include <string>
using namespace std;
class Pet
{
public:
    Pet(string theName);
    void eat();
    void sleep();
    virtual void play();

protected:
    string name;
};

class Cat : public Pet
{
public :
    Cat(string theName);
    void climb();
    void play();
};

class Dog : public Pet
{
public:
    Dog(string theName);
    void bark();
    void play();
};

Pet::Pet(string theName)
{
    name = theName;
}
void Pet::eat()
{
    cout << name <<  "[正在吃东西]" << endl;
}

void Pet::sleep()
{
    cout << name << "[正在睡大觉]" << endl;
}
void Pet::play()
{
    cout << name << "[正在玩]" << endl;
}

Cat::Cat(string theName) : Pet(theName)
{
}

void Cat::climb()
{
    cout << name << "[正在爬树]" << endl;
}
void Cat::play()
{
    Pet::play();
    cout << name << "[玩毛线球]" << endl;
}

Dog::Dog(string theName) : Pet(theName)
{

}

void Dog::bark()
{
    cout << name << "[旺 旺 旺]" << endl;
}

void Dog::play()
{
    Pet::play();
    cout << name <<  "[正在追赶那只猫]" << endl;
}

int main()
{
    int *p = new int;
    *p = 100;
    cout << *p << endl;
    delete p;

    Pet *cat = new Cat("加菲");
    Pet *dog = new Dog("欧迪");

    cat->sleep();
    cat->eat();
    cat->play();

    dog->sleep();
    dog->eat();
    dog->play();

    delete dog;
    delete cat;

    return 0;
}