// file: ClassB.h

#ifndef CLASSB_H_INCLUDED
#define CLASSB_H_INCLUDED

// defenition for the function

typedef int (*FUNCTION)(int x, int y);

class ClassB
{
public:
  void SetFunction(FUNCTION func);
  void DoSomething();
private:
  FUNCTION func;
};

#endif // CLASSB_H_INCLUDED

  

  
// file: ClassA.h

#ifndef CLASSA_H_INCLUDED
#define CLASSA_H_INCLUDED

#include "ClassB.h"

class ClassA
{
public:
  ClassA();
  TheFunction(int x, int y);
};

#endif // CLASSA_H_INCLUDED

  

  
// file: ClassB.cpp


#include "ClassB.h"

// sets the function variable

void ClassB::SetFunction(FUNCTION func)
{
  this->func = func;
}

// calls our function variable

void ClassB::DoSomething()
{
  func(5,5);
}
  

  
// file: ClassA.cpp


#include "ClassA.h"

ClassA::ClassA()
{
  // initialize ClassB and set the function to TheFunction

  ClassB classB;
  // here is the problem

  classB.SetFunction(TheFunction);
  classB.DoSomething();
}

// the actual function

int ClassA::TheFunction(int x, int y)
{
  return(x + y);
}
  

  class ClassC{public:    ClassC();    TheOtherFunction(int x, int y);};// somewhere in a cpp file...B.SetFunction(A.TheFunction); // this worksB.SetFunction(C.TheOtherFunction); // this doesnt work