Comp201: Principles of Object-Oriented Programming I
Spring 2008 -- Union Design Pattern: Inheritance and Polymorphism   

Encapsulation, Inheritance and Polymorphism constitute the three fundamental concepts in object-oriented programming.  Using an abstract class to represent the union of all its subclasses expresses inheritance in the most comprehensive way and exploits polymorphism in the most elegant and effective manner.   As such, Inheritance and Polymorphism are two sides of the same coin.  In spite of its foundational importance, the OO pattern community takes this design for granted and does not even have a name for it.  Here, we give it a name: the Union Design Pattern.

This lecture continues on the Connexions web site.