Question

I need to map some state to a particular member function of a class, for (a very cut down) example:

class Z {
   _a_ptr_to_some_member _p;

   void UpdateGuiForStopState(State s) {
      // do something with state
   }

   Z() {
      // setup _p to point to UpdateGuiForStopState
   }

   void StateComesInHere(State s) {
      if(s.id == STOP_ID) { // eventually use lookup
         _p(s);
      }
   }
}

Using just the STL (can’t use third party stuff like boost), What is the type of _a_ptr_to_some_member and how do I bind the method UpdateGuiForStopState to it?

Presumably I use the stl mem_xxx stuff but can’t work out how.

And yes I can do this a hundred and one other different ways, but I want to work out if this way is possible.

Answer 1

Using STL’s bind1st and mem_fun:

class Z3 {
   typedef std::mem_fun1_t<void,Z3,State> _a_ptr_to_some_member_raw;
   typedef std::binder1st<_a_ptr_to_some_member_raw> _a_ptr_to_some_member;
   _a_ptr_to_some_member _p;

   void UpdateGuiForStopState(State s) {
      // do something with state
   }

   Z3() : _p(std::bind1st(std::mem_fun(&Z3::UpdateGuiForStopState), this))
   {
   }

   void StateComesInHere(State s) {
      if(s.id == STOP_ID) { // eventually use lookup
         _p(s);
      }
   }
};