Review By: Mark L. Johns
04/22/2005"Refactoring to Patterns" by Joshua Kerievsky is an exceptional book that serves well as a reference and tutorial guide on using refactoring processes combined with pattern techniques. I found "Refactoring To Patterns" to be an informative and thought provoking book. One might even get a better understanding of the book by reading Martin Fowler's "Refactoring," which Kerievsky suggests his work is based upon. Once I read Fowler's book, I found that it was easier to understand Kerievsky's examples.

The book begins with the author explaining why he wrote the book and the metamorphosis he went through as he learned more by utilizing patterns in his daily work. He then delves into refactoring and patterns, devoting a complete chapter to each. In these chapters, Kerievsky defines the concepts, backgrounds, and benefits.

After laying the groundwork and educating the reader, the author dives into "Code Smells" that can be used to reveal if your code needs to be refactored. Twelve different design smells are detailed, preparing the reader to "deodorize" any code.

Chapter 5 formulates the refactoring patterns used in the book. These formulas are very similar in format to those used by Martin Fowler in his book "Refactoring." The remaining chapters (6 through 11) compose a catalog of twenty-seven examples based upon the author's real-world coding efforts that has been enhanced by input from other programmers.

Kereivsky's examples are probably the greatest strength and weakness of the book. The examples are straight from the real world and are highly detailed. His approach is methodical and incremental. But I also had to do further research to understand the full scope of the example. At times, I found myself having to study other references to understand what was going on. This only happens a couple of times and is probably unavoidable given the universe of real-world examples versus real-world experiences.

One of the most refreshing aspects of this book is the author's attitude toward the topic. Kerievsky's attitude borders on skepticism at times about the use of patterns. Based upon his personal experience, he talks about over-engineering designs and forcing patterns onto lightweight projects where they aren't needed and shouldn't really be used. He mentions Agile programming and even works the concept of continuous testing into the book.

I consider both of these, to be huge "wins" for the Quality Assurance and Quality Control area. Methodology/Process for process sake and the lack of support for testing during development have always been issues. With this text, Kerievsky will hopefully be able to coax those that fear the methodology into trying it and making intra-process testing a part of normal practice.

"Refactoring Patterns" is a great companion book or add-on to Martin Fowlers' "Refactoring." This book is a must-have for any programmer wanting to understand and improve their knowledge on software design or redesign.