Object-Oriented Thought Process, The, Second Edition

Why Design Patterns?

The concept of design patterns did not necessarily start with the need for reusable software. In fact, the seminal work on design patterns is about constructing buildings and cities. As Christopher Alexander noted in A Pattern Language: Towns, Buildings, Construction: “Each pattern describes a problem which occurs over and over again in our environment, and then describes the core of the solution to that problem, in such a way that you can use the solution a million times over, without ever doing it the same way twice.”

The Four Elements of a Pattern

The GoF describe a pattern as having four essential elements:

• The pattern name is a handle we can use to describe a design problem, its solutions, and consequences in a word ...