How to define a general member function pointer

Question

I have created a Timer class that must call a callback method when the timer has expired. Currently I have it working with normal function pointers (they are declared as void (

Answer 1

Dependencies, dependencies... yeah, sure boost is nice, so is mem_fn, but you don't need them. However, the syntax of calling member functions is evil, so a little template magic helps:

   class Callback
   {
   public:
      void operator()() { call(); };
      virtual void call() = 0;
   };

   class BasicCallback : public Callback
   {
      // pointer to member function
      void (*function)(void);
   public:
      BasicCallback(void(*_function)(void))
          : function( _function ) { };
      virtual void call()
      { 
          (*function)();
      };
   };   

   template  
   class ClassCallback : public Callback
   {
      // pointer to member function
      void (AnyClass::*function)(void);
      // pointer to object
      AnyClass* object;        
   public:
      ClassCallback(AnyClass* _object, void(AnyClass::*_function)(void))
          : object( _object ), function( _function ) { };
      virtual void call()
      { 
          (*object.*function)();
      };
   };

Now you can just use Callback as a callback storing mechanism so:

void set_callback( Callback* callback );
set_callback( new ClassCallback( my_class, &MyClass::timer ) );

And

Callback* callback = new ClassCallback( my_class, &MyClass::timer ) );

(*callback)();
// or...
callback->call();