C++语言基础例程多态性的概念

- 日理万妓 2022-01-27 14:13 188阅读 0赞

[贺老师的教学链接][Link 1] [本课讲解][Link 2]

一种死板的机制

#include <iostream>
    #include <string>
    using namespace std;
    //声明基类Student
    class Student
    {
    public:
        Student(int, string,float);//声明构造函数
        void display( );                                             //声明输出函数
    protected:                                      //受保护成员，派生类可以访问
        int num;
        string name;
        float score;
    };
    //Student类成员函数的实现
    Student::Student(int n, string nam,float s)
    {
        num=n;    //定义构造函数
        name=nam;
        score=s;
    }
    
    
    void Student::display( )                                        //定义输出函数
    {
        cout<<"num:"<<num<<"\nname:"<<name<<"\nscore:"<<score<<"\n\n";
    }
    //声明公用派生类Graduate
    class Graduate:public Student
    {
    public:
        Graduate(int, string, float, float);                          //声明构造函数
        void display( );                                             //声明输出函数
    private:
        float pay;
    };
    // Graduate类成员函数的实现
    void Graduate::display( )                                       //定义输出函数
    {
        cout<<"num:"<<num<<"\nname:"<<name<<"\nscore:"<<score<<"\npay="<<pay<<endl;
    }
    
    
    Graduate::Graduate(int n, string nam,float s,float p):Student(n,nam,s),pay(p) { }
    
    
    //主函数
    int main()
    {
        Student stud1(1001,"Li",87.5);                   //定义Student类对象stud1
        Graduate grad1(2001,"Wang",98.5,563.5);          //定义Graduate类对象grad1
        Student *pt=&stud1;                              //定义指向基类对象的指针变量pt
        pt->display( );
        pt=&grad1;
        pt->display( );
        return 0;
    }

运行中的动态是这样的！

#include <iostream>
    #include <string>
    using namespace std;
    //声明基类Student
    class Student
    {
    public:
        Student(int, string,float);//声明构造函数
        virtual void display( );                                             //声明输出函数
    protected:                                      //受保护成员，派生类可以访问
        int num;
        string name;
        float score;
    };
    //Student类成员函数的实现
    Student::Student(int n, string nam,float s)
    {
        num=n;    //定义构造函数
        name=nam;
        score=s;
    }
    
    
    void Student::display( )                                        //定义输出函数
    {
        cout<<"num:"<<num<<"\nname:"<<name<<"\nscore:"<<score<<"\n\n";
    }
    //声明公用派生类Graduate
    class Graduate:public Student
    {
    public:
        Graduate(int, string, float, float);                          //声明构造函数
        void display( );                                             //声明输出函数
    private:
        float pay;
    };
    // Graduate类成员函数的实现
    void Graduate::display( )                                       //定义输出函数
    {
        cout<<"num:"<<num<<"\nname:"<<name<<"\nscore:"<<score<<"\npay="<<pay<<endl;
    }
    
    
    Graduate::Graduate(int n, string nam,float s,float p):Student(n,nam,s),pay(p) { }
    
    
    //主函数
    int main()
    {
        Student stud1(1001,"Li",87.5);                   //定义Student类对象stud1
        Graduate grad1(2001,"Wang",98.5,563.5);          //定义Graduate类对象grad1
        Student *pt=&stud1;                              //定义指向基类对象的指针变量pt
        pt->display( );
        pt=&grad1;
        pt->display( );
        return 0;
    }

[Link 1]: http://blog.csdn.net/sxhelijian/article/details/8001601
[Link 2]: http://edu.csdn.net/course/detail/474/5169