Question

Possible Duplicate:
How to force child same virtual function call its parent virtual function first

I have a class hierarchy where each derived class overrides a given virtual function and starts its implementation by calling the one in its parent class. The goal is to have each of the derived implementation to be executed, but I do not like the way I do it.

For example, I have this class:

class base
{
public:
  void do_stuff() { do_something(); }
  virtual void do_something() { }
};

Then I derive this class on several levels:

class derived_10:
  public derived_9 // which inherit from derived_8 and so on until derived_0
                   // which inherit from base
{
public:
  virtual void do_something()
  {
    // this will also call derived_8::do_something() and so on
    // until base::do_something()
    derived_9::do_something();

    // then, some stuff
  }
};

I’m looking for a solution that will make sure that all derived_x::do_something() will be called in sequence when base::do_stuff() is called, without having to expect the derived classes to do this themselves. Do you have an idea of the best way to get this behavior ?

Answer 1

I’ve already asked a very similar question before: Calling overriden class methods as a chain in C++

The answer I’ve accepted pointed at your own solution. I can give you an idea about an alternative though. Constructors and destructors already have this behavior in C++, you might want to consider restructuring your code, so that the work is done during the construction or the destruction of an object that belongs to a class in a hierarchy. I’m not sure you’ll be able to make this worth the effort though. On the other hand, you never know what you can get out of some template metaprogramming + some preprocessor magic.