Refactoring: Improving the Design of Existing Code (Addison-Wesley Signature Series (Fowler))

by Martin Fowler

“Improving the design after it has been written.” That’s an odd turn of phrase. For much of the history of software development, most people believed that we design first, and only when done with design should we code. Over time, the code will be modified, and the integrity of the system—its structure according to that design—gradually fades. The code slowly sinks from engineering to hacking. Refactoring is the opposite of this practice. With refactoring, we can take a bad, even chaotic, design and rework it into well-structured code. Each step is simple—even simplistic. I move a field from one class to another, pull some code out of a method to make it into its own method, or push some code up or down a hierarchy. Yet the cumulative effect of these small changes can radically improve the design. It is the exact reverse of the notion of software decay.