C++之virtual 方法

1、例子1

  

   

    

     

    
    

     

      #include <iostream>
     
    
   

    

     

    
    

     

      class A
     
    
   

    

     

    
    

     

      {
     
    
   

    

     

    
    

     

      public:
     
    
   

    

     

    
    

     

       const char* fetchClassName() { return "A"; }
     
    
   

    

     

    
    

     

      };
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     

      class B: public A
     
    
   

    

     

    
    

     

      {
     
    
   

    

     

    
    

     

      public:
     
    
   

    

     

    
    

     

       const char* fetchClassName() { return "B"; }
     
    
   

    

     

    
    

     

      };
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     

      int main(void)
     
    
   

    

     

    
    

     

      {
     
    
   

    

     

    
    

     

         B obj_b;
     
    
   

    

     

    
    

     

         A &obj_a = obj_b;
     
    
   

    

     

    
    

     

         std::cout << obj_a.fetchClassName() << "\n";
     
    
   

    

     

    
    

     

      }
     
    
  
 

运行结果
A

2、例子2

  

   

    

     

    
    

     

      #include <iostream>
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     

      class A
     
    
   

    

     

    
    

     

      {
     
    
   

    

     

    
    

     

      public:
     
    
   

    

     

    
    

     

       virtual const char* fetchClassName() { return "A"; }
     
    
   

    

     

    
    

     

      };
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     

      class B: public A
     
    
   

    

     

    
    

     

      {
     
    
   

    

     

    
    

     

      public:
     
    
   

    

     

    
    

     

       virtual const char* fetchClassName() { return "B"; }
     
    
   

    

     

    
    

     

      };
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     

      int main(void)
     
    
   

    

     

    
    

     

      {
     
    
   

    

     

    
    

     

         B obj_b;
     
    
   

    

     

    
    

     

         A &obj_a = obj_b;
     
    
   

    

     

    
    

     

         std::cout << obj_a.fetchClassName() << "\n";
     
    
   

    

     

    
    

     

      }
     
    
  
 

运行结果
B

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原文链接：chenyu.blog.csdn.net/article/details/62891875