970ee117   
   From: daniel.kruegler@googlemail.com   
      
   Am 16.10.2011 15:29, schrieb Ethan:   
   >   I'm trying to have a member function of a class to be a friend of   
   > another class, however, i get this error   
   > Am i missing anything?   
      
   You are missing that for a friend declaration to another class's member   
   function the other class must be complete at the point of the friend   
   declaration.   
      
   > main.cpp:10: error: invalid use of incomplete type ‘struct B’   
   > main.cpp:3: error: forward declaration of ‘struct B’   
   >   
   > #include   
   >   
   > class B;   
   >   
   > class A {   
   > int a;   
   > public : A() { a = 5; }   
   >          void sample(B);   
   >          friend void B::sample();   
   > };   
   >   
   > class B {   
   > public : void sample() {   
   >              //printf("%d\n",obj.a);   
   >          }   
   > };   
      
   This requires a redesign to make this well-formed, e.g.   
      
   #include    
      
   class A;   
      
   class B {   
   public :   
      void sample();   
   };   
      
   class A {   
   int a;   
   public : A() { a = 5; }   
      void sample(B);   
      friend void B::sample();   
   };   
      
   void B::sample() {   
      //printf("%d\n",obj.a);   
   }   
      
   HTH & Greetings from Bremen,   
      
   - Daniel Krügler   
      
      
      
      
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