I prefer to not populate my hash during the construction phase, but use a separate method for that. The reason is multiple inheritance. If you do multiple inheritance, it will be that at least one of the constructors isn't called, or that the object from at least one of the constructors (assuming you are using 2 classes - it's worse with more) won't survive. If both constructors return populated objects, the inheriting class needs to break encapsulation, and construct a resulting object by mucking with the internals. It becomes a lot easier if you have a separate method to (initially) populate your objects.