C++ Polymorphism practice

在上一题的基础上

For the Product hierarchy of PE 4.12, suppose that,once a month,the chain runs an application that contains the loop

            for(int i = 0;i<productCount;i++) 

                   products[i]->adjustPrice();

where products is an array of pointers to the base class Produst ,which has a virtual method adjustPrice.The virtual method adjusts the price of each Produst at least 10 classes from Produst,overriding the sdjustPrice in each.Implement a test alient that uses sample data to test the hierarchy.

多态是一种运行期绑定机制，也是讲函数名称动态的绑定到函数入口地址的运行期绑定机制

也就是说这题需要使用多态 因为有很多产品 要调用priceChange（）函数 

多态的使用前提条件：

1.必须存在一个继承体系结构。

2.继承体系结构中的一些类必须具有同名的virtual成员函数（virtual is a keyword）。

3.至少有一个基类类型的指针或者基类类型的引用，这个指针或引用可用来对virtual成员函数进行调用。

* 当声明了基类的一个成员函数为虚函数后，该成员函数在所有派生类中也将自动成为虚函数。

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代码如下：

#include<iostream>
#include<string>

using namespace std;

class Product{
public:
    int supply,demand;
    double p;
  
    Product(){};
        Product(string na):name(na){
        };
        Product(string na,double pri):name(na),price( pri){
        };
        Product(string na,double pri,int da):name( na),price( pri),date(da){
        };
        void Input();
        void Output();        
        void setSupply();
        void setDemand();
        void setPrice();
        virtual void adjustPrice(); 
        

private:
        string name;
        double price;
        int date;
        string manuf;
        

};



class Fruit: public Product{
    
};
class Dairy:public Product{
    
};
class Meat:public Product{
};


class Cuke:public Fruit{
    public:
    
        void adjustPrice()
        {
            
                if(supply>demand)
            {
            p=p*0.95;
                cout<<"output the changed price:"<<endl;
            cout << p<<endl;
            }
            if(supply=demand)
            {
                p=p*1.0;
                    cout<<"output the changed price:"<<endl;
                cout<< p<<endl;
            }
            
            if(supply<demand)
            {
                p=p*2.0;
                    cout<<"output the changed price:"<<endl;
                cout<<p<<endl;
            }    
        }
       

    };
class Apple:public Fruit{
     public:
    
       
         void adjustPrice()
        {
            
                if(supply>demand)
            {
            p=p*0.95;
                cout<<"output the changed price:"<<endl;
            cout << p<<endl;
            }
            if(supply=demand)
            {
                p=p*1.0;
                    cout<<"output the changed price:"<<endl;
                cout<< p<<endl;
            }
            
            if(supply<demand)
            {
                p=p*2.0;
                    cout<<"output the changed price:"<<endl;
                cout<<p<<endl;
            }    
        }
       
};
class Lemon:public Fruit{
     public:
    
         void adjustPrice()
        {
            
                if(supply>demand)
            {
            p=p*0.95;
                cout<<"output the changed price:"<<endl;
            cout << p<<endl;
            }
            if(supply=demand)
            {
                p=p*1.0;
                    cout<<"output the changed price:"<<endl;
                cout<< p<<endl;
            }
            
            if(supply<demand)
            {
                p=p*2.0;
                    cout<<"output the changed price:"<<endl;
                cout<<p<<endl;
            }    
        }
       
};
class Orange:public Fruit{
     public:
    
         void adjustPrice()
        {
            
                if(supply>demand)
            {
            p=p*0.95;
                cout<<"output the changed price:"<<endl;
            cout << p<<endl;
            }
            if(supply=demand)
            {
                p=p*1.0;
                    cout<<"output the changed price:"<<endl;
                cout<< p<<endl;
            }
            
            if(supply<demand)
            {
                p=p*2.0;
                    cout<<"output the changed price:"<<endl;
                cout<<p<<endl;
            }    
        }
       
};
class Butter:public Dairy{
    public:
    
       void adjustPrice()
        {
            
                if(supply>demand)
            {
            p=p*0.95;
                cout<<"output the changed price:"<<endl;
            cout << p<<endl;
            }
            if(supply=demand)
            {
                p=p*1.0;
                    cout<<"output the changed price:"<<endl;
                cout<< p<<endl;
            }
            
            if(supply<demand)
            {
                p=p*2.0;
                    cout<<"output the changed price:"<<endl;
                cout<<p<<endl;
            }    
        }
       
        
        
};
class Milk:public Dairy{
    public:
    
        void adjustPrice()
        {
            
                if(supply>demand)
            {
            p=p*0.95;
                cout<<"output the changed price:"<<endl;
            cout << p<<endl;
            }
            if(supply=demand)
            {
                p=p*1.0;
                    cout<<"output the changed price:"<<endl;
                cout<< p<<endl;
            }
            
            if(supply<demand)
            {
                p=p*2.0;
                    cout<<"output the changed price:"<<endl;
                cout<<p<<endl;
            }    
        }
        
};
class Yogurt:public Dairy{
     public:
    
        void adjustPrice()
        {
            
                if(supply>demand)
            {
            p=p*0.95;
                cout<<"output the changed price:"<<endl;
            cout << p<<endl;
            }
            if(supply=demand)
            {
                p=p*1.0;
                    cout<<"output the changed price:"<<endl;
                cout<< p<<endl;
            }
            
            if(supply<demand)
            {
                p=p*2.0;
                    cout<<"output the changed price:"<<endl;
                cout<<p<<endl;
            }    
        }
       
};
class Beef:public Meat{
    public:
        
        void adjustPrice()
        {
            
                if(supply>demand)
            {
            p=p*0.95;
                cout<<"output the changed price:"<<endl;
            cout << p<<endl;
            }
            if(supply=demand)
            {
                p=p*1.0;
                    cout<<"output the changed price:"<<endl;
                cout<< p<<endl;
            }
            
            if(supply<demand)
            {
                p=p*2.0;
                    cout<<"output the changed price:"<<endl;
                cout<<p<<endl;
            }    
        }
      
        
};
class Pork:public Meat{ 
    public:
    
         void adjustPrice()
        {
            
                if(supply>demand)
            {
            p=p*0.95;
                cout<<"output the changed price:"<<endl;
            cout << p<<endl;
            }
            if(supply=demand)
            {
                p=p*1.0;
                    cout<<"output the changed price:"<<endl;
                cout<< p<<endl;
            }
            
            if(supply<demand)
            {
                p=p*2.0;
                    cout<<"output the changed price:"<<endl;
                cout<<p<<endl;
            }    
        }
       
};
class Fish:public Meat{
     public:
    
    void adjustPrice()
        {
            
                if(supply>demand)
            {
            p=p*0.95;
                cout<<"output the changed price:"<<endl;
            cout << p<<endl;
            }
            if(supply=demand)
            {
                p=p*1.0;
                    cout<<"output the changed price:"<<endl;
                cout<< p<<endl;
            }
            
            if(supply<demand)
            {
                p=p*2.0;
                    cout<<"output the changed price:"<<endl;
                cout<<p<<endl;
            }    
        }
       
};


void Product :: Input()
{
    cout << "input name:"<< endl;
    
    getline(cin,name);

    cout << "input price:"<< endl;
    
    cin >> price;
     

    
    cout << "input date:" << endl;
     
    cin >>  date;

}
void Product :: Output()
{
    string st;
    cout<< "input the information you want:"<< endl;
    cout << "name,price,date "<<endl;
    cin >> st;
    if(st == "name" )
    
        cout << name <<endl;
    
    if(st =="price")
    
        cout << price << endl;
    
    if(st == "date")
    
        cout << date << endl;
    
}

void Product::setSupply()
        {
    
            
            cout<<"input the supply:"<<endl;
            cout<<"low=-1,medium=0,high=1"<<endl;
            cin >> supply;
        }
void Product::setDemand()
        {
        
            cout<<"input the demand:"<<endl;
            cout<<"low=-1,medium=0,high=1"<<endl;
            cin >> demand;
            }
void Product::setPrice()
{
    cout<<"input the price"<<endl;
    cin >> p;
}
 void Product::adjustPrice()
        {
                if(supply>demand)
            {
            p=p*0.95;
                cout<<"output the changed price:"<<endl;
            cout << p<<endl;
            }
            if(supply=demand)
            {
                p=p*1.0;
                    cout<<"output the changed price:"<<endl;
                cout<< p<<endl;
            }
            
            if(supply<demand)
            {
                p=p*2.0;
                    cout<<"output the changed price:"<<endl;
                cout<<p<<endl;
            }    
        }
int main()
{
    Product p1;
    p1.Input();
    p1.Output();
    Cuke p2;
    p2.setDemand();
    p2.setSupply();
    p2.setPrice();
    p2.adjustPrice();
   
    Product *products[10];//设置一个指向基类的指针数组 
    Cuke pro0;//使Pro0具有Cuke属性
    Apple pro1;
    Lemon pro2;
    Orange pro3;
    Butter pro4;
    Milk pro5;
    Yogurt pro6;
    Beef pro7;
    Pork pro8;
    Fish pro9;
    
    products[0]=&pro0;//将pro0 也就是cuke的地址给products[0]
    products[1]=&pro1;
    products[2]=&pro2;
    products[3]=&pro3;
    products[4]=&pro4;
    products[5]=&pro5;
    products[6]=&pro6;
    products[7]=&pro7;
    products[8]=&pro8;
    products[9]=&pro9;
    
    for(int i=0;i<10;i++)
449     products[i]->adjustPrice();
  
453     return 0;
}