面向对象编程的四大特性（C++）

面向对象编程的四大特性：

• 封装
• 抽象
• 继承
• 多态

1. 封装
   C++中，将数据和对数据的操作（函数）封装成一个叫“类（class）”的结构体。

   class Rectangle
   {protected:int width, height;       //数据public:Shape(int a=0, int b=0){width=a;height=b;}int area()           //对数据的操作{cout << "Rectangle::area()" << endl;return (width*height);}
   };

    

2. 继承
   一个类可以继承另一个类，形成继承关系，又称父子关系。

   class Shape
   {protected:int width, height;public:Shape(int a=0, int b=0){width=a;height=b;}virtual int area() = 0;
   };class Rectangle:public Shape  //Rectangle继承了Shape，Rectangle为子类/派生类，Shape为父类/基类
   {public:Rectangle(int a=0, int b=0):Shape(a,b){}int area(){cout << "Rectangle::area()" << endl;return (width*height);}
   };

   
   

3. 多态
   父类的（纯）虚函数被子类继承和重载，实现其特有的功能。不同的子类可以有不同的实现。这种现象称为多态。
   

4. 抽象
   接口和实现分离，称为抽象。例如，父类的（纯）虚函数就是接口，子类对虚函数的重载为实现。
   

   #include <iostream>
   using namespace std;class Shape  //抽象类
   {protected:int width, height;public:Shape(int a=0, int b=0){width=a;height=b;}virtual int area() = 0;   //接口
   };class Rectangle:public Shape
   {public:Rectangle(int a=0, int b=0):Shape(a,b){}int area(){cout << "Rectangle::area()" << endl;return (width*height);}
   };class Triangle:public Shape
   {public:Triangle(int a=0,int b=0):Shape(a,b){}int area(){cout << "Triangle::area()" << endl;return (width*height)/2;}
   };int main()
   {Shape * shape;Rectangle rec(10,7);Triangle tri(10,5);//多态shape = &rec;shape->area();  //Rectangle::area()shape = &tri;shape->area();  //Triangle::area()return 0;
   }