Ranga Vadlamudi

How to Use Design Patterns
A Conversation with Erich Gamma, Part I
by Bill Venners
May 23, 2005

Summary
Among developers, design patterns are a popular way to think about design, but what is the proper way to think about design patterns? In this interview, Erich Gamma, co-author of the landmark book, Design Patterns, talks with Bill Venners about the right way to think about and use design patterns.

Observer Design Pattern

The Observer design pattern defines a one-to-many dependency between a subject object and a number of observer objects so that when the subject changes state, all its observers are notified and updated automatically.