C++:C++的两种多态形式

 1 //
 2 //  main.cpp
 3 //  Test.cpp
 4 //
 5 //  Created by mac on 15/8/11.
 6 //  Copyright (c) 2015年. All rights reserved.
 7 //
 8 #include<iostream>
 9 #include<cstring>
10 using namespace std;
11 class Person    //基类Person
12 {
13 private:
14     string  name;
15     int age;
16 public:
17     Person();
18     virtual ~Person();//虚析构函数
19     Person(string name,int age);
20     void setname(string name);
21     void setage(int age);
22     virtual void show();//虚成员函数,子类继承后必须要重写该函数
23     //virtual void show()=0;//纯虚函数,此时该类就不能创建对象了。
24 };
25 Person::Person(){};
26 Person::Person(string name,int age)
27 {
28     this->name = name;
29     this->age = age;
30 }
31 void Person::setname(string name)
32 {
33     this->name = name;
34 }
35 void Person::setage(int age)
36 {
37     this->age = age;
38 }
39 void Person::show()
40 {
41     cout<<"name:"<<name<<","<<"age:"<<age<<endl;
42 }
43 Person::~Person(){};
47 class Student:public Person//基类Person的公有派生类Studnet 48 { 49 private: 50 float score; 51 string subject; 52 public: 53 Student(); 54 virtual ~Student();//virtual可加可不加 55 virtual void show();//virtual可加可不加 56 Student(string name,int age,float score,string subject); 57 }; 58 Student::Student(){}; 59 Student::Student(string name,int age,float score,string subject):Person(name,age) 60 { 61 this->score = score; 62 this->subject = subject; 63 } 64 void Student::show() 65 { 66 Person::show(); 67 cout<<"score:"<<score<<","<<"subject:"<<subject<<endl; 68 } 69 Student::~Student(){}; 70 int main(int argc, const char * argv[]) 71 { 72 Person p; 73 p.setname("xiayuanquan"); 74 p.setage(23); 75 p.show(); 76 77 Student stu("lisi",23,98.5,"English"); 78 stu.show(); 79 80 //多态的特性(例1)父类的引用指向子类对象 81 Person person; 82 Student st("chenglong",60,99,"chinese"); 83 person = st; 84 st.show(); 85 86 //多态的特性(例2)父类的指针指向子类对象 87 Person *p2 = new Student("zhangsan",20,100,"math"); 88 p2->show(); 89 90 return 0; 91 }

   程序运行结果:

name:xiayuanquan,age:23
name:lisi,age:23
score:98.5,subject:English
name:chenglong,age:60
score:99,subject:chinese
name:zhangsan,age:20
score:100,subject:math
Program ended with exit code: 0

总结:实现多态的三个条件:

1.存在继承关系

2.多态的第一种,父类的引用指向子类对象 或者 多态的第二种,父类的指针指向子类对象。

3.子类必须要重写父类的同名方法

posted @ 2015-08-11 17:31  XYQ全哥  阅读(725)  评论(0编辑  收藏  举报