Dynamic functors with references

ref_function.cpp

#include <boost/function.hpp>
#include <boost/ref.hpp>
#include <iostream>

class X {
public:
  void foobar() {
    // do stuff 
    // if func_ is set, call it
    if(func_) { func_(23); }
  }
 
  template<typename Functor>
  void set_on_foobar(Functor f) { func_ = f; }
 
  void remove_on_foobar() { func_ = boost::function<int(int)>(); }
private:
  boost::function<void(int)> func_;
};

struct my_f {
  my_f(int i):i_(i){}
  ~my_f(){std::cout << "destructed" << std::endl;}
  void operator()(int x) const { std::cout << "Operator() " << x+i_ << "\n"; } 
  int i_;
};
 
int main()
{
  X x;
  my_f f(7);
  x.set_on_foobar(boost::ref(f)); // with a functor
  x.foobar();
  f.i_=100;
  x.foobar();
  return 0;
}