C++ 运行时多态

#include<iostream>
using namespace std;


class AbstractDrinking
{
//存在纯虚函数，则类是抽象类（即无法实例化对象）
public:
    //纯虚函数，可以仅有声明
    virtual void boil() =0;//煮水
    
    virtual void brew() =0;//冲泡
    
    virtual void putSomethingElse()=0;//加入辅料
    
    void makeDrink()
{
        boil();
        brew();
        putSomethingElse();
    }
    
    AbstractDrinking()
    {
        cout<<"AbstractDrinking类 构造函数调用"<<endl;
    }
    //虚析构的写法
//    virtual ~AbstractDrinking()
//    {
//        cout<<"AbstractDrinking类 虚析构函数调用"<<endl;
//    }

    //纯虚析构，不能仅有声明
    virtual ~AbstractDrinking() = 0;
};

  //纯虚析构的定义，不能仅有声明
AbstractDrinking::~AbstractDrinking()
{
    cout<<"AbstractDrinking类 纯虚析构函数调用"<<endl;
}



class Coffee: public AbstractDrinking
{
public:
    Coffee()
    {
        cout<<"Coffee类 构造函数调用"<<endl;
    }

    virtual void boil()//重写抽象基类虚函数
{
        cout<<"煮开水";
        cout<<"（水温"<<* temperature<<"摄氏度）"<<endl;
    }

    virtual void brew()//重写抽象基类虚函数
{
        cout<<"倒入咖啡"<<endl;
    }

    virtual void putSomethingElse()//重写抽象基类虚函数
{
        cout<<"放入咖啡伴侣"<<endl;
    }

    void makeDrink()
{
        boil();
        brew();
        putSomethingElse();
    }
    
    virtual ~Coffee()
    {
        cout<<"Coffee类 析构函数调用"<<endl;
        //写析构函数的作用是用来释放堆区数据
        //若类内没有创建堆区数据，可不用写析构函数
        if(temperature != NULL)
        {
            delete temperature;
            temperature = NULL;
        }
    }
private:
    float * temperature = new float(100);//堆区数据
    
};


class Tea: public AbstractDrinking
{
public:
    Tea()
    {
        cout<<"Tea类 构造函数调用"<<endl;
    }
    virtual void boil()
{
        cout<<"煮热水";
        cout<<"（水温"<<* temperature<<"摄氏度）"<<endl;
    }

    virtual void brew()
{
        cout<<"倒入茶叶"<<endl;
    }

    virtual void putSomethingElse()
{
        cout<<"放入枸杞"<<endl;
    }

    void makeDrink()
{
        boil();
        brew();
        putSomethingElse();
    }


    virtual ~Tea()
    {
        cout<<"Tea类 析构函数调用"<<endl;
        if(temperature != NULL)
        {
            delete temperature;
            temperature = NULL;
        }
    }
private:
    float * temperature = new float(90);//堆区数据
    
};



void makeDrink(AbstractDrinking* abs)
{
    abs->makeDrink();
    delete abs;//使用完成后须释放堆区数据
    cout<<"----------------------------\n"<<endl;
}


int main()
{
    //AbstractDrinking* abs = new Coffee;
    //makeDrink(abs);
    //delete abs;


    //abs = new Tea;
    //makeDrink(abs);
    //delete abs;


    //AbstractDrinking absd;//error: cannot declare variable 'absd' to be of abstract type 'AbstractDrinking'|

    //子类指针传给抽象基类指针形参
    makeDrink(new Coffee);
    makeDrink(new Tea);

    return 0;
}