纯虚函数和抽象类

分手后的思念是犯贱 2023-07-09 14:25 75阅读 0赞

一个拥有纯虚函数的基类被称为抽象类。

## 基本概念 ##

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3RpYW5ndWl5dXl1_size_16_color_FFFFFF_t_70][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3RpYW5ndWl5dXl1_size_16_color_FFFFFF_t_70 1][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3RpYW5ndWl5dXl1_size_16_color_FFFFFF_t_70 2][]

## 5.2抽象类案例 ##

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3RpYW5ndWl5dXl1_size_16_color_FFFFFF_t_70 3][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3RpYW5ndWl5dXl1_size_16_color_FFFFFF_t_70 4][]

代码如下：

#include <iostream>
    using namespace std;
    
    面向抽象类编程(面向一套预先定义好的接口编程)
    
    //解耦合 ....模块的划分
    
    
    class  Figure //抽象类
    {
    public:
    	//阅读一个统一的界面(接口),让子类使用,让子类必须去实现
    	virtual void getArea() = 0 ; //纯虚函数
    protected:
    private:
    };
    
    class Circle : public Figure
    {
    public:
    	Circle(int a, int b)
    	{
    		this->a = a;
    		this->b = b;
    	}
    	virtual void getArea()
    	{
    		cout<<"圆形的面积: "<<3.14*a*a<<endl;;
    
    	}
    
    private:
    	int a;
    	int b;
    };
    
    class Tri : public Figure
    {
    public:
    	Tri(int a, int b)
    	{
    		this->a = a;
    		this->b = b;
    	}
    	virtual void getArea() 
    	{
    		cout<<"三角形的面积: "<<a*b/2<<endl;;
    	}
    
    private:
    	int a;
    	int b;
    };
    
    
    class Square : public Figure
    {
    public:
    	Square(int a, int b)
    	{
    		this->a = a;
    		this->b = b;
    	}
    	virtual void getArea() 
    	{
    		cout<<"四边形的面积: "<<a*b<<endl;;
    	}
    
    private:
    	int a;
    	int b;
    };
    
    
    void objplay(Figure *base)
    {
    	base->getArea(); //会发生多态
    }
    
    
    void main511()
    {
    
    	//Figure f; //抽象类不能被实例化
    
    	Figure *base = NULL; //抽象类不能被实例化
    
    	Circle c1(10, 20);
    	Tri t1(20, 30);
    	Square s1(50, 60);
    
    	//面向抽象类编程(面向一套预先定义好的接口编程)
    
    	objplay(&c1);
    	objplay(&t1);
    	objplay(&s1);
    
    	//c1.getArea();
    	
    	cout<<"hello..."<<endl;
    	system("pause");
    	return ;
    }

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