C ++ virtual functions list polymorphic - polymorphism simple use

 

First look at the code below, create a parent class, then subclass inherits the parent class in to one, two class has its own play () method, in the first 35-37 lines of code to create a parent pointer then subclass address assignment by reference to the parent class, then call the pointer P play () method will print out what yet. I thought it would be a subclass of calling play () method, because to quote the line 36, but the print result is:

　　This play is a parent class

. 1 #include <the iostream>
 2  
. 3  class Father
 . 4  {
 . 5  public :
 . 6      void play ()
 . 7      {
 . 8          STD :: COUT << " This is the play of a parent class " << STD :: endl;
 . 9      }
 10  };
 . 11  
12 is  class Son: public Father
 13 is  {
 14  public :
 15      void Play ()
 16      {
 . 17          STD :: COUT << " this is subclasses Play" << std::endl;
18     }
19 };
20 
21 
22 void party(Father** men, int num)
23 {
24     for (int i = 0; i < num; i++)
25     {
26         men[i]->play();
27     }
28 }
29 
30 int main()
31 {
32     Father father;
33     Son son;
34 
35     Father* p;            //A pointer P is defined parent class 
36      P = & Son;             // pointer references subclass address 
37 [      p-> play ();             // play accessing pointers () method, the access will be play subclass () it? 
38 is  
39 }

 

 

Access method in the subclass of parent class through a pointer, this situation often encountered in the project. If you want to access a subclass method pointer by a parent class in how to do it? Just add a keyword before the relevant parent class method: virtual 

The following code:

. 1 #include <the iostream>
 2  
. 3  class Father
 . 4  {
 . 5  public :
 . 6      virtual  void play ()                                         // in the parent class play () method of increasing virtual keyword before 
. 7      {
 . 8          STD :: COUT << " This is a parent class Play " << STD :: endl;
 . 9      }
 10  };
 . 11  
12 is  class Son: public Father
 13 is  {
 14  public :
 15      void Play ()
16     {
17         std::cout << "这是个子类的Play" << std::endl;
18     }
19 };
20 
21 
22 void party(Father** men, int num)
23 {
24     for (int i = 0; i < num; i++)
25     {
26         men[i]->play();
27     }
28 }
29 
30 int main()
31 {
32     Father father;
33 is      Son Son;
 34 is  
35      Father * P;             // pointer to a parent class definition P 
36      P = & Son;             // pointer references subclass address 
37 [      p-> Play ();             // Play accessing pointers () method, the visit will be the play subclass () Why? 
38 is  
39 }

 

Operating results as follows:

　　This is a sub-class of Play

 

 

 

 

 

 

 

 

 

==========================================================================================================================