The Art of Agile Development

Simple Design

Note

Programmers

Our design is easy to modify and maintain.

Perfection is achieved, not when there is nothing more to add, but when there is nothing left to take away. —Antoine de Saint-Exupéry, author of The Little Prince

Any intelligent fool can make things bigger, more complex and more violent. It takes a touch of genius and a lot of courage to move in the opposite direction. —Albert Einstein

When writing code, agile developers often stop to ask themselves, “What is the simplest thing that could possibly work?” They seem to be obssessed with simplicity. Rather than anticipating changes and providing extensibility hooks and plug-in points, they create a simple design that anticipates as little as possible, as cleanly as possible. Unintuitively, this results in designs that are ready for any change, anticipated or not.

This may seem silly. How can a design be ready for any change? Isn’t the job of a good designer or architect to anticipate future changes and make sure the design can be extended to support them? Doesn’t Design Patterns: Elements of Reusable Software say that the key to maximizing reuse is to anticipate changes and design accordingly?

I’ll let Erich Gamma, coauthor of Design Patterns, answer these questions. In the following excerpt, Gamma is interviewed by Bill Venners.^[49]

Venners: The GoF book [Design Patterns] says, “The key to maximizing reuse lies in anticipating new requirements and changes to existing requirements, and in designing your systems so they ...