Having a class function call a function outside the class

This is a bit hard to explain, and i'm not even sure this is possible in C++, but here it goes.

Imagine I have a class "Level" for a tetris game. One function in this class is called "CheckLines" and it checks if there are any lines in the level and then removes them.

In the main program I have another function, "onLineFound", which, for example, plays a sound effect and adds 10 point to the score.

Now everytime "CheckLines" finds a line, I want it to call "onLineFound", but I do not want "onLineFound" to be part of the "Level" class (because the class is platform independent and playing a sound is not).

Note that I could solve this particular example in other ways, but I'm looking for the method, not the solution :)

-Aeroren

The method is to ensure there is a prototype for the function you wish to call visible to the compiler at the point you wish to call it.

Code:

---

void onLineFound();  //  this declaration may be in a header file

void Level::CheckLines()
{
    onLineFound();

  // equivalent to above, but more explicit

  ::onLineFound();
}

---

The above assumes both the class member function and the function being called accept no arguments and return void.

You could use a callback function, via function pointers. However, a better solution (in my opinion) would be to write your method as a functor (a struct with overloaded operator( ) to behave like a function), and pass that to your class. If swapping the function out is no issue, then use grumpy's solution.