C++虚成员函数

和普通的成员函数一样，虚成员函数同样可以被继承。我们只需要将基类中的display函数通过virtual关键字声明为虚函数，之后即使在派生类中display函数声明时未加上virtual关键字，但它在所有的派生类中都将自动成为虚函数。

#include<iostream>
using namespace std;

class base
{
public:
   virtual  void hello(){cout<<"Hello base!"<<endl;}
};

class derived: public base
{
public:
    //void hello(){cout<<"Hello derived!"<<endl;}
};

class derivedson: public derived
{
    void hello(){cout<<"Hello derivedson!"<<endl;}
};

int main()
{
	
    base * p = new base;
    p->hello();
    delete p;
    p = new derived;
    p->hello();
    delete p;
    derived * pp = new derivedson;
    pp->hello();
    delete pp;
    return 0;
}

Hello base!
Hello base!
Hello derivedson!