C++ function pointers and classes

Question

Say I have:

void Render(void(*Call)())
{
    D3dDevice->BeginScene();
    Call();
    D3dDevice->EndScene();
    D3dDevice->Present(0,0,0,0);
}

This is fine as long as the function I want to use to render is a function or a static member function:

Render(MainMenuRender);
Render(MainMenu::Render);

However, I really want to be able to use a class method as well since in most cases the rendering function will want to access member variables, and Id rather not make the class instance global, e.g.

Render(MainMenu->Render);

However I really have no idea how to do this, and still allow functions and static member functions to be used.

Answer 1

There are a lot of ways to skin this cat, including templates. My favorite is Boost.function as I've found it to be the most flexible in the long run. Also read up on Boost.bind for binding to member functions as well as many other tricks.

It would look like this:

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

void Render(boost::function0<void> Call)
{
    // as before...
}

Render(boost::bind(&MainMenu::Render, myMainMenuInstance));

Answer 2

You can make a wrapper function void Wrap(T *t) that just calls t->Call() and have Render take such a function together with an object. That is:

void Wrap(T *t)
{
  t->Call();
}

void Render(void (*f)(T *), T *t)
{
  ...
  f(t);
  ...
}