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：

  1 #include<iostream>
  2 #include<string>
  3 
  4 using namespace std;
  5 
  6 class Product{
  7 public:
  8     int supply,demand;
  9     double p;
 10   
 11     Product(){};
 12         Product(string na):name(na){
 13         };
 14         Product(string na,double pri):name(na),price( pri){
 15         };
 16         Product(string na,double pri,int da):name( na),price( pri),date(da){
 17         };
 18         void Input();
 19         void Output();        
 20         void setSupply();
 21         void setDemand();
 22         void setPrice();
 23         virtual void adjustPrice(); 
 24         
 25 
 26 private:
 27         string name;
 28         double price;
 29         int date;
 30         string manuf;
 31         
 32 
 33 };
 34 
 35 
 36 
 37 class Fruit: public Product{
 38     
 39 };
 40 class Dairy:public Product{
 41     
 42 };
 43 class Meat:public Product{
 44 };
 45 
 46 
 47 class Cuke:public Fruit{
 48     public:
 49     
 50         void adjustPrice()
 51         {
 52             
 53                 if(supply>demand)
 54             {
 55             p=p*0.95;
 56                 cout<<"output the changed price:"<<endl;
 57             cout << p<<endl;
 58             }
 59             if(supply=demand)
 60             {
 61                 p=p*1.0;
 62                     cout<<"output the changed price:"<<endl;
 63                 cout<< p<<endl;
 64             }
 65             
 66             if(supply<demand)
 67             {
 68                 p=p*2.0;
 69                     cout<<"output the changed price:"<<endl;
 70                 cout<<p<<endl;
 71             }    
 72         }
 73        
 74 
 75     };
 76 class Apple:public Fruit{
 77      public:
 78     
 79        
 80          void adjustPrice()
 81         {
 82             
 83                 if(supply>demand)
 84             {
 85             p=p*0.95;
 86                 cout<<"output the changed price:"<<endl;
 87             cout << p<<endl;
 88             }
 89             if(supply=demand)
 90             {
 91                 p=p*1.0;
 92                     cout<<"output the changed price:"<<endl;
 93                 cout<< p<<endl;
 94             }
 95             
 96             if(supply<demand)
 97             {
 98                 p=p*2.0;
 99                     cout<<"output the changed price:"<<endl;
100                 cout<<p<<endl;
101             }    
102         }
103        
104 };
105 class Lemon:public Fruit{
106      public:
107     
108          void adjustPrice()
109         {
110             
111                 if(supply>demand)
112             {
113             p=p*0.95;
114                 cout<<"output the changed price:"<<endl;
115             cout << p<<endl;
116             }
117             if(supply=demand)
118             {
119                 p=p*1.0;
120                     cout<<"output the changed price:"<<endl;
121                 cout<< p<<endl;
122             }
123             
124             if(supply<demand)
125             {
126                 p=p*2.0;
127                     cout<<"output the changed price:"<<endl;
128                 cout<<p<<endl;
129             }    
130         }
131        
132 };
133 class Orange:public Fruit{
134      public:
135     
136          void adjustPrice()
137         {
138             
139                 if(supply>demand)
140             {
141             p=p*0.95;
142                 cout<<"output the changed price:"<<endl;
143             cout << p<<endl;
144             }
145             if(supply=demand)
146             {
147                 p=p*1.0;
148                     cout<<"output the changed price:"<<endl;
149                 cout<< p<<endl;
150             }
151             
152             if(supply<demand)
153             {
154                 p=p*2.0;
155                     cout<<"output the changed price:"<<endl;
156                 cout<<p<<endl;
157             }    
158         }
159        
160 };
161 class Butter:public Dairy{
162     public:
163     
164        void adjustPrice()
165         {
166             
167                 if(supply>demand)
168             {
169             p=p*0.95;
170                 cout<<"output the changed price:"<<endl;
171             cout << p<<endl;
172             }
173             if(supply=demand)
174             {
175                 p=p*1.0;
176                     cout<<"output the changed price:"<<endl;
177                 cout<< p<<endl;
178             }
179             
180             if(supply<demand)
181             {
182                 p=p*2.0;
183                     cout<<"output the changed price:"<<endl;
184                 cout<<p<<endl;
185             }    
186         }
187        
188         
189         
190 };
191 class Milk:public Dairy{
192     public:
193     
194         void adjustPrice()
195         {
196             
197                 if(supply>demand)
198             {
199             p=p*0.95;
200                 cout<<"output the changed price:"<<endl;
201             cout << p<<endl;
202             }
203             if(supply=demand)
204             {
205                 p=p*1.0;
206                     cout<<"output the changed price:"<<endl;
207                 cout<< p<<endl;
208             }
209             
210             if(supply<demand)
211             {
212                 p=p*2.0;
213                     cout<<"output the changed price:"<<endl;
214                 cout<<p<<endl;
215             }    
216         }
217         
218 };
219 class Yogurt:public Dairy{
220      public:
221     
222         void adjustPrice()
223         {
224             
225                 if(supply>demand)
226             {
227             p=p*0.95;
228                 cout<<"output the changed price:"<<endl;
229             cout << p<<endl;
230             }
231             if(supply=demand)
232             {
233                 p=p*1.0;
234                     cout<<"output the changed price:"<<endl;
235                 cout<< p<<endl;
236             }
237             
238             if(supply<demand)
239             {
240                 p=p*2.0;
241                     cout<<"output the changed price:"<<endl;
242                 cout<<p<<endl;
243             }    
244         }
245        
246 };
247 class Beef:public Meat{
248     public:
249         
250         void adjustPrice()
251         {
252             
253                 if(supply>demand)
254             {
255             p=p*0.95;
256                 cout<<"output the changed price:"<<endl;
257             cout << p<<endl;
258             }
259             if(supply=demand)
260             {
261                 p=p*1.0;
262                     cout<<"output the changed price:"<<endl;
263                 cout<< p<<endl;
264             }
265             
266             if(supply<demand)
267             {
268                 p=p*2.0;
269                     cout<<"output the changed price:"<<endl;
270                 cout<<p<<endl;
271             }    
272         }
273       
274         
275 };
276 class Pork:public Meat{ 
277     public:
278     
279          void adjustPrice()
280         {
281             
282                 if(supply>demand)
283             {
284             p=p*0.95;
285                 cout<<"output the changed price:"<<endl;
286             cout << p<<endl;
287             }
288             if(supply=demand)
289             {
290                 p=p*1.0;
291                     cout<<"output the changed price:"<<endl;
292                 cout<< p<<endl;
293             }
294             
295             if(supply<demand)
296             {
297                 p=p*2.0;
298                     cout<<"output the changed price:"<<endl;
299                 cout<<p<<endl;
300             }    
301         }
302        
303 };
304 class Fish:public Meat{
305      public:
306     
307     void adjustPrice()
308         {
309             
310                 if(supply>demand)
311             {
312             p=p*0.95;
313                 cout<<"output the changed price:"<<endl;
314             cout << p<<endl;
315             }
316             if(supply=demand)
317             {
318                 p=p*1.0;
319                     cout<<"output the changed price:"<<endl;
320                 cout<< p<<endl;
321             }
322             
323             if(supply<demand)
324             {
325                 p=p*2.0;
326                     cout<<"output the changed price:"<<endl;
327                 cout<<p<<endl;
328             }    
329         }
330        
331 };
332 
333 
334 void Product :: Input()
335 {
336     cout << "input name:"<< endl;
337     
338     getline(cin,name);
339 
340     cout << "input price:"<< endl;
341     
342     cin >> price;
343      
344 
345     
346     cout << "input date:" << endl;
347      
348     cin >>  date;
349 
350 }
351 void Product :: Output()
352 {
353     string st;
354     cout<< "input the information you want:"<< endl;
355     cout << "name,price,date "<<endl;
356     cin >> st;
357     if(st == "name" )
358     
359         cout << name <<endl;
360     
361     if(st =="price")
362     
363         cout << price << endl;
364     
365     if(st == "date")
366     
367         cout << date << endl;
368     
369 }
370 
371 void Product::setSupply()
372         {
373     
374             
375             cout<<"input the supply:"<<endl;
376             cout<<"low=-1,medium=0,high=1"<<endl;
377             cin >> supply;
378         }
379 void Product::setDemand()
380         {
381         
382             cout<<"input the demand:"<<endl;
383             cout<<"low=-1,medium=0,high=1"<<endl;
384             cin >> demand;
385             }
386 void Product::setPrice()
387 {
388     cout<<"input the price"<<endl;
389     cin >> p;
390 }
391  void Product::adjustPrice()
392         {
393                 if(supply>demand)
394             {
395             p=p*0.95;
396                 cout<<"output the changed price:"<<endl;
397             cout << p<<endl;
398             }
399             if(supply=demand)
400             {
401                 p=p*1.0;
402                     cout<<"output the changed price:"<<endl;
403                 cout<< p<<endl;
404             }
405             
406             if(supply<demand)
407             {
408                 p=p*2.0;
409                     cout<<"output the changed price:"<<endl;
410                 cout<<p<<endl;
411             }    
412         }
413 int main()
414 {
415     Product p1;
416     p1.Input();
417     p1.Output();
418     Cuke p2;
419     p2.setDemand();
420     p2.setSupply();
421     p2.setPrice();
422     p2.adjustPrice();
423    
424     Product *products[10];//设置一个指向基类的指针数组 
425     Cuke pro0;//使Pro0具有Cuke属性
426     Apple pro1;
427     Lemon pro2;
428     Orange pro3;
429     Butter pro4;
430     Milk pro5;
431     Yogurt pro6;
432     Beef pro7;
433     Pork pro8;
434     Fish pro9;
435     
436     products[0]=&pro0;//将pro0 也就是cuke的地址给products[0]
437     products[1]=&pro1;
438     products[2]=&pro2;
439     products[3]=&pro3;
440     products[4]=&pro4;
441     products[5]=&pro5;
442     products[6]=&pro6;
443     products[7]=&pro7;
444     products[8]=&pro8;
445     products[9]=&pro9;
446     
447     for(int i=0;i<10;i++)
448 449     products[i]->adjustPrice();
450   
452 453     return 0;
454 }