Boost C++. Passing a member function pointer with signature pointer to function

Question

The question may be a bit confusing, but the concept is relatively simple.

I have a function that is passed any given non-static class method and object pointer, and binds these to yield a simple function pointer (see code below),

I have a particular signature (return type void, one argument of type int), that I wish the method to be:

header file:

//method_pointer.hpp
#include <boost/bind.hpp>
#include <boost/function.hpp>

class A
{
  public:
    void aMethod( int );
};


class B
{
  public:
    template < class T >
    B( boost::function< void ( int ) > method_ptr,
       T * obj_ptr )
    {
      bCallAMethod( boost::bind( method_ptr, obj_ptr, _1 ) );
    }

    void bCallAMethod( boost::function< void (int ) > );
};

source file:

// method_pointer.cpp
#include <cstdio>

#include "method_pointer.hpp"

void A::aMethod( int x )
{
  printf("My number: %d\n", x);
}

void B::bCallAMethod( boost::function<void ( int ) > method_ptr )
{
  method_ptr( 5 );
}

int main( void )
{
  A a;
  B b( &A::aMethod, &a );
  return 1;
}

The main code instantiates an object of class A; then instantiates an object of class B by passing a method and instance of A to the constructor. B should then be able to call the method in A by this boost::function.

I know how to do this if I know which method is being passed in (eg &A::aMethod), but the goal is to generalize to any method with that signature.

I am getting the compilation error

$ g++ method_pointer.cpp -lboost_system -lrt
method_pointer.cpp: In function ‘int main()’:
method_pointer.cpp:18:11: error: invalid use of non-static member function ‘void A::aMethod(int)’

Any ideas?

I'm also open to being consistent and using some boost function for the class template if possible.

Answer 1

You need to change B constructor's prototype to :

template<typename T>
B (void (T::*method_ptr)(int), T * obj_ptr)