std::function for member functions

We can use std::function to work with a member function. We should just specify the class type for the input function in the template for the std::function. In a way, that is an explicit representation of the "this" pointer that would be used internally to access the relative object.

Since it is possible to pass the relative object in three ways (by value, by reference, by pointer) we should also specify that information in the std::function declaration.

If your compiler does not support std::function yet, you could get the same result using boost::function - just changing a couple of lines in the examples:

#include <iostream>

// boost version
//#include "boost/function.hpp"
//using boost::function;

// C++0x version
#include <functional>
using std::function;

namespace
{
   class AClass
   {
   public:
      void doStuff(int i) const
      {
         std::cout << "Stuff done: " << i << std::endl;
      }
   };
}

void function03()
{
   std::cout << "Member function, class object by value" << std::endl;
   function<void(AClass, int)> f1;
   f1 = &AClass::doStuff;
   f1(AClass(), 1);

   std::cout << "Member function, class object by reference" << std::endl;
   function<void(AClass&, int)> f2;
   f2 = &AClass::doStuff;
   AClass ac2;
   f2(ac2, 2);

   std::cout << "Member function, class object by pointer" << std::endl;
   function<void(AClass*, int)> f3;
   f3 = &AClass::doStuff;
   AClass ac3;
   f3(&ac3, 3);
}

The code is based on an example provided by "Beyond the C++ Standard Library: An Introduction to Boost", by Björn Karlsson, an Addison Wesley Professional book. An interesting reading indeed.