Bearded-android-docs

Created Tuesday 15 October 2013

Inheritance vs Composition

• http://stackoverflow.com/questions/49002/prefer-composition-over-inheritance
• http://lostechies.com/chadmyers/2010/02/13/composition-versus-inheritance/

Summary: there is no better or worse principle. There's only "appropriate" and "inadequate" design for the given task. However, in general, prefer composition.

• Use the Liskov Substitution Principle to determine if you should use inheritance.
• Composition represents a "has a/uses a" relationship. Ex: A car has an engine. (Alternatively, does Type B only want some of the methods of Type A?)
• Inheritance is a "behaves likes a" relationship. (Alternatively, does Type B want to use all the public methods of Type A such that Type B can be used wherever Type A is expected?)