Gang of Four (GoF)

Design patterns in computer science achieved prominence when Design Pattern: Elements of Reusable Object-Oriented Software was published in 1994 by authors Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides. These authors are also known as the Gang of Four (GoF).

This book contains 23 classic design patterns. After this book, many programmers adopted and created their own design patterns, referring to these classic patterns as bases.

Instead of memorizing exact classes, methods, and properties in design patterns, it is very important to understand the concept and where to apply it appropriately. Incorrect, unsuitable, or unnecessary usage of design patterns can over complicate your code and may result in code that is hard to maintain and debug.

Note

A design pattern is a tool. As with any tool, its performance depends on its usage and the user who is using it.

Gang of Four design patterns are divided into the following three categories:

• The creational pattern
• The structural pattern 
• The behavioral pattern

The following figure shows a summary of the design patterns and their categories: