6.3 虚函数
#include <iostream.h>
#include <string.h>
class student
{public:
student (int n,string nam, float s)
{ num= n; name= nam; score= s; }
void display( )
{cout<<“num:”<<num
<<“name:”<<name
<<“score:”<<score<<endl; }
protected:
int num; string name; float score;
};
class graduate : public student
{public:
graduate (int n, string nam, float s, float p):
student (n,nam,s), pay(p) { }
void display( )
{cout<<“num:”<<num
<<“name:”<<name
<<“score:”<<score
<<“pay:”<<pay<<endl; }
private:
float pay;
};
void main( )
{ student s1(1001,”Li”,98.5);
graduate g1(2001,”Liu”,90.5,800.5);
student * pt = &s1;
pt->display( ); // 指向基类对象s1
pt = &g1;
pt->display( ); // 指向派生类对象g1,仅
输出了派生类的基类数据成员，因为它
调用的是基类成员函数display!
}
假如想输出派生类的全部数据，当然可以采用下面两种方法之一：
通过派生类对象名g1，调用派生类对象的成员函数：g1.display( )；
定义一个指向派生类的指针ptr，并指向g1，然后用ptr->display( )。
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