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Message:

Composition Versus Inheritance

Posted by Bruce Blackshaw on 18 Oct 1998, 10:46 AM

Bill,

I feel this is a timely & useful article. Programmers new to OO (which includes
a lot of Java programmers) often tend to go overboard when they
discover inheritance & virtual functions.

Unless you clearly have a "is-a" relationship, composition should be
one of the first options considered in OO design(IMO).

Code maintenance can be an absolute nightmare if a programmer has used
complicated inheritance hierarchies when composition may well have
been more appropriate in places.

All this highlights the importance of a good OO design process. The
more upfront design, the more maintainable the result. As an aside,
I've recently been using UML's object sequence diagrams in the
design process & have been suprised at how useful the technique has been.

Bruce Blackshaw
London, UK