2.2孙鑫C++

1、继承

 动物有 吃 睡 呼吸的方法 当然 鱼也有    不用重复再定义

　　1）public 那里都可以访问

#include <iostream.h>
class Animal //类 基类
{
public:
    void eat()//吃方法
    {
    cout<<"animal eat "<<endl;

    }
    void sleep()//睡觉方法
    {
        cout<<"animal sleep"<<endl;
    }
    void breathe()//呼吸方法
    {
        cout<<"animal breathe"<<endl;
    }
};
class Fish: public Animal//  //子类
{


};

void main()

{
    Animal an;
    an.eat();
    Fish fh;
    fh.sleep();
}

　　2）protected 只有子类能访问   外部其他的都不能被访问

　　　　

#include <iostream.h>
class Animal //类 基类
{
public:
    void eat()//吃方法
    {
    cout<<"animal eat "<<endl;

    }
protected:
    void sleep()//睡觉方法
    {
        cout<<"animal sleep"<<endl;
    }
    void breathe()//呼吸方法
    {
        cout<<"animal breathe"<<endl;
    }
};
class Fish: public Animal//  //子类
{
    void test()
    {
        sleep();
        breathe();
    }

};

void main()

{
    Animal an;
    an.eat();
    Fish fh;
    fh.sleep();
}

　　3）private 只有自己能访问 ，子类 外部都不能访问

#include <iostream.h>
class Animal //类 基类
{
public:
    void eat()//吃方法
    {
    cout<<"animal eat "<<endl;

    }
protected:
    void sleep()//睡觉方法
    {
        cout<<"animal sleep"<<endl;
    }
private:
    void breathe()//呼吸方法
    {
        cout<<"animal breathe"<<endl;
    }
};
class Fish: public Animal//  //子类
{
    void test()
    {
        sleep();
        breathe();
    }

};

void main()

{
    Animal an;
    an.eat();
    Fish fh;
//    fh.sleep();
}

　　4）访问特性

　　

 

　　　　最多为public继承

2、继承的先后性

　　没有父亲 就没有孩子

　　1）基类 子类 构造函数的调用顺序

         动物先

#include <iostream.h>
class Animal //类 基类
{
public:
    
    Animal()
    {
        cout<<"Animal construct "<<endl;
    }
    void eat()//吃方法
    {
    cout<<"animal eat "<<endl;

    }
//protected:
    void sleep()//睡觉方法
    {
        cout<<"animal sleep"<<endl;
    }
//private:
    void breathe()//呼吸方法
    {
        cout<<"animal breathe"<<endl;
    }
};
class Fish: public Animal// 继承特性 //子类
{
public:
    Fish()
    {
        cout<<"Fish construct "<<endl;
    }

};

void main()

{
//    Animal an;
//    an.eat();
    Fish fh;
//    fh.sleep();
}

　　2）基类 子类 析构函数的调用顺序

　　  鱼先

#include <iostream.h>
class Animal //类 基类
{
public:
    
    Animal()
    {
        cout<<"Animal construct "<<endl;
    }
    ~Animal()
    {
        cout<<"Animal deconstruct "<<endl;
    }
    void eat()//吃方法
    {
    cout<<"animal eat "<<endl;

    }
//protected:
    void sleep()//睡觉方法
    {
        cout<<"animal sleep"<<endl;
    }
//private:
    void breathe()//呼吸方法
    {
        cout<<"animal breathe"<<endl;
    }
};
class Fish: public Animal// 继承特性 //子类
{
public:
    Fish()
    {
        cout<<"Fish construct "<<endl;
    }
    ~Fish()
    {
        cout<<"Fish deconstruct "<<endl;
    }
};

void main()

{
//    Animal an;
//    an.eat();
    Fish fh;
//    fh.sleep();
}

　　

3、继承出错：没有对象的基类  子类初始化  基类没有初始化  且基类有参数

   子类只能初始化无 参数的  基类

　　错误：无 缺省的 基类可条用

#include <iostream.h>
class Animal //类 基类
{
public:
    
    Animal(int height , int weight)
    {
        cout<<"Animal construct "<<endl;
    }
    ~Animal()
    {
        cout<<"Animal deconstruct "<<endl;
    }
    void eat()//吃方法
    {
    cout<<"animal eat "<<endl;

    }
//protected:
    void sleep()//睡觉方法
    {
        cout<<"animal sleep"<<endl;
    }
//private:
    void breathe()//呼吸方法
    {
        cout<<"animal breathe"<<endl;
    }
};
class Fish: public Animal// 继承特性 //子类
{
public:
    Fish()
    {
        cout<<"Fish construct "<<endl;
    }
    ~Fish()
    {
        cout<<"Fish deconstruct "<<endl;
    }
};

void main()

{
//    Animal an;
//    an.eat();
    Fish fh;
//    fh.sleep();
}

　　解决：象基类中传递参数   Fish():Animal(400,300)

#include <iostream.h>
class Animal //类 基类
{
public:
    
    Animal(int height , int weight)
    {
        cout<<"Animal construct "<<endl;
    }
    ~Animal()
    {
        cout<<"Animal deconstruct "<<endl;
    }
    void eat()//吃方法
    {
    cout<<"animal eat "<<endl;

    }
//protected:
    void sleep()//睡觉方法
    {
        cout<<"animal sleep"<<endl;
    }
//private:
    void breathe()//呼吸方法
    {
        cout<<"animal breathe"<<endl;
    }
};
class Fish: public Animal// 继承特性 //子类
{
public:
    Fish():Animal(400,300)
    {
        cout<<"Fish construct "<<endl;
    }
    ~Fish()
    {
        cout<<"Fish deconstruct "<<endl;
    }
};

void main()

{
//    Animal an;
//    an.eat();
    Fish fh;
//    fh.sleep();
}

　　4）常量初始化

　　

class Fish: public Animal// 继承特性 //子类
{
public:
    Fish():Animal(400,300),a(1)
    {
//        cout<<"Fish construct "<<endl;
    }
    ~Fish()
    {
//        cout<<"Fish deconstruct "<<endl;
    }
private :
    const int a;
};

4、函数的覆盖

　　1）不要基类的

　　父亲结婚：花轿

　　儿子击婚：轿车

#include <iostream.h>
class Animal //类 基类
{
public:
    
    Animal(int height , int weight)
    {
    //    cout<<"Animal construct "<<endl;
    }
    ~Animal()
    {
    //    cout<<"Animal deconstruct "<<endl;
    }
    void eat()//吃方法
    {
    cout<<"animal eat "<<endl;

    }
//protected:
    void sleep()//睡觉方法
    {
        cout<<"animal sleep"<<endl;
    }
//private:
    void breathe()//呼吸方法
    {
        cout<<"animal breathe"<<endl;
    }
};
class Fish: public Animal// 继承特性 //子类
{
public:
    Fish():Animal(400,300),a(1)
    {
//        cout<<"Fish construct "<<endl;
    }
    ~Fish()
    {
//        cout<<"Fish deconstruct "<<endl;
    }
    void sleep()
    {
        cout<<"jjjjjjjjjj"<<endl;
    }
private :
    const int a;
};

void main()

{
//    Animal an;
//    an.eat();
    Fish fh;
    fh.sleep();
}

　　1）两个都要

　　父亲结婚：花轿

　　儿子击婚：轿车 花轿

#include <iostream.h>
class Animal //类 基类
{
public:
    
    Animal(int height , int weight)
    {
    //    cout<<"Animal construct "<<endl;
    }
    ~Animal()
    {
    //    cout<<"Animal deconstruct "<<endl;
    }
    void eat()//吃方法
    {
    cout<<"animal eat "<<endl;

    }
//protected:
    void sleep()//睡觉方法
    {
        cout<<"animal sleep"<<endl;
    }
//private:
    void breathe()//呼吸方法
    {
        
        cout<<"animal breathe"<<endl;
    }
};
class Fish: public Animal// 继承特性 //子类
{
public:
    Fish():Animal(400,300),a(1)
    {
//        cout<<"Fish construct "<<endl;
    }
    ~Fish()
    {
//        cout<<"Fish deconstruct "<<endl;
    }
    void sleep()
    {
        Animal::sleep();
        cout<<"jjjjjjjjjj"<<endl;
    }
private :
    const int a;
};

void main()

{
//    Animal an;
//    an.eat();
    Fish fh;
    fh.sleep();
}

5、对象转换

　　类型转换

　　int--char 丢失精度  截掉了三个字节

     char--int  ok 允许

　　对象转换：

　　　　内存模型相同才能转换

输出的是 动物的 而不是 鱼的

#include <iostream.h>
class Animal //类 基类
{
public:
    
    Animal(int height , int weight)
    {
    //    cout<<"Animal construct "<<endl;
    }
    ~Animal()
    {
    //    cout<<"Animal deconstruct "<<endl;
    }
    void eat()//吃方法
    {
    cout<<"animal eat "<<endl;

    }
//protected:
    void sleep()//睡觉方法
    {
        cout<<"animal sleep"<<endl;
    }
//private:
    void breathe()//呼吸方法
    {
        
        cout<<"animal breathe"<<endl;
    }
};
class Fish: public Animal// 继承特性 //子类
{
public:
    Fish():Animal(400,300),a(1)
    {
//        cout<<"Fish construct "<<endl;
    }
    ~Fish()
    {
//        cout<<"Fish deconstruct "<<endl;
    }
    void sleep()
    {
        Animal::sleep();//作用域标示符
        cout<<"jjjjjjjjjj"<<endl;
    }
private :
    const int a;
};
void fn(Animal *pAn)
{
    pAn->sleep();
}
void main()

{
//    Animal an;
//    an.eat();
    Fish fh;
    Animal *pAn;
    pAn=&fh;
    fn(pAn);
//    fh.sleep();
}