From: Paul <pdavidow@...>
Date: 2007-12-14T07:40:00+09:00
Subject: Enforce implementation of Module method

Let's say I have the following module:

------------------------
module Parenting

  def add_child(a_child)
    self.children.push(a_child)
  end

  def delete_child(a_child)
    self.children.delete(a_child)
  end

  def children
    # need to implement
  end

end
------------------------

Is there a way to enforce that the 'children' method is implemented in
any class which includes this module?  Or do I simply rely on a
commenting convention, as above?