C++语言基础 例程 基类与派生类的转换

贺老师的教学链接  本课讲解

指向基类对象的指针变量也可以指向派生类对象

#include <iostream>#include <string>using namespace std;class Student//声明Student类{public:    Student(int, string,float);    void display( );private:    int num;    string name;    float score;};Student::Student(int n, string nam,float s){    num=n;    name=nam;    score=s;}void Student::display( ){    cout<<endl<<"num:"<<num<<endl;    cout<<"name:"<<name<<endl;    cout<<"score:"<<score<<endl;}class Graduate:public Student{public:    Graduate(int, string ,float,float);    void display( );private:    float pay;};Graduate::Graduate(int n, string nam,float s,float p):Student(n,nam,s),pay(p) { }void Graduate::display(){    Student::display();    cout<<"pay="<<pay<<endl;}int main(){    Student stud1(1001,"Li",87.5);    Graduate grad1(2001,"Wang",98.5,563.5);    Student *pt=&stud1;    pt->display( );    pt=&grad1;    pt->display( );    return 0;}