#include <iostream>
using namespace std;
class A //A是一个抽象类,不能new A直接实例化.
{
public:
virtual void out1()=0; //纯虚函数:由子类实现
virtual ~A(){};
virtual void out2() //虚函数:默认实现
{
cout<<"A(out2)"<<endl;
}
void out3() //普通函数:强制实现
{
cout<<"A(out3)"<<endl;
}
};
class B:public A
{
public:
//virtual ~B(){};
void out1()//纯虚函数:由子类实现
{
cout<<"B(out1)"<<endl;
}
void out2()//虚函数:默认实现
{
cout<<"B(out2)"<<endl;
}
void out3()
{
cout<<"B(out3)"<<endl;
}
};
int main()
{
/*多态:1.父类指针指向子类对象(不可倒过来.)
2.虚函数与纯虚函数确实调用子类的重写(覆盖)的函数,普通函数还是调用父类函数.
*/
A *ab = new B();
ab->out1();//子类实现父类的纯虚函数,此时调用子类out1()
ab->out2();//子类重写(覆盖)父类的虚函数,此时调用子类out2()
ab->out3();//父类是普通函数，没有多态功能.
cout<<"************************"<<endl;
B *bb = new B();
bb->out1();
bb->out2();
bb->out3();
cout<<"************************"<<endl;
B cc;
cc.out1();
cc.out2();
cc.out3();
cout<<"************************"<<endl;
//A是一个抽象类,不能new A直接实例化.错误写法
/*
A dd = new A;
dd.out1();
dd.out2();
dd.out3();
*/
delete ab;
delete bb;
return 0;
}
