虚函数——多态的关键
一、未使用虚函数的继承
a)父类与子类定义
class Father
{
public:
Father(){}
~Father(){}
void print(){cout<<"这是父类：Father"<<endl;}
};
class Clild_A:public Father
{
void print(){cout<<"这是子类：Child_A"<<endl;}
};
class Clild_B:public Father
{
void print(){cout<<"这是子类：Child_B"<<endl;}
};
b)全局函数print()
void print( Father &theFather)
{
theFather.print();
}
c)主函数
int _tmain(int argc, _TCHAR* argv[])
{
Father *theFather_A=new Clild_A();
Father *theFather_B=new Clild_B();
print(*theFather_A);
print(*theFather_B);
delete theFather_A;
delete theFather_B;
system("pause");
return 0;
}
运行结果：
二、使用了虚函数的继承——多态
a)父类与子类定义
class Father
{
public:
Father(){}
virtual ~Father(){}//保证父类指针指向子类时,delete基类指针,子类的析构行为能正确调用
virtual void print(){cout<<"这是父类：Father"<<endl;}
};
class Clild_A:public Father
{
virtual void print(){cout<<"这是子类：Child_A"<<endl;}
};
class Clild_B:public Father
{
virtual void print(){cout<<"这是子类：Child_B"<<endl;}
};
b)全局函数print()
void print( Father &theFather)
{
theFather.print();
}
c)主函数
int _tmain(int argc, _TCHAR* argv[])
{
Father *theFather_A=new Clild_A();
Father *theFather_B=new Clild_B();
print(*theFather_A);
print(*theFather_B);
delete theFather_A;
delete theFather_B;
system("pause");
return 0;
}
运行结果：
注:a)Virtual 用来告诉系统，遇到这个处理过程要等到执行时再确定到底调用哪个类的处理过程
b)多态的两大核心：1）虚函数
2）父类引用指向子类（使得在添加新类时，print方法无需修改）
三、面向过程实现等价功能的繁琐处理
需要在全局print函数中，用switch区分出传递进来的分别是哪个子类，然后调用各个子类
相应print方法；
而且以后每增加一个子类，就要修改全局print函数
附: 虚函数与纯虚函数对比
