Refactoring: Improving the Design of Existing Code

I've known about this book for over a year. Initially, I thought it was about re-engineering legacy systems. I don't do that, so I didn't give it much thought. Over the past year, I have stumbled across repeated references to this book. Everyone seems to cite it, and now I understand why. It's very easy to fall into 'analysis paralysis' when doing object design. A commonly heard complaint is "I have created 27 different class diagrams, and 42 separate sequence diagrams, but I can't seem to get any code written..." XP's popularity is due, in part, becuase it get's you into action--you begin writing code immediately, instead of creating diagrams for weeks (or months) on end. XP's motto could be "just do it!"But how does one reconcile this "code first, ask questions later" mentality with an acknowledged need to at least do some design work? In "Refactoring", Martin Fowler provides the answer. His prescription is to create some code to get something working, then look at the code to see how it might be improved-- refactor it. In Fowler's view, you won't really understand the problem until you have coded it, so instead of spending the next three weeks trying to find the perfect pattern for your next task, forget the pattern, and get some code going. Once you've got something workable, then think about patterns you might back into from your existing code.Of course, that's a gross oversimplification of the process, but it gives a flavor of the ready-fire-aim process that 'Refactoring' is built around. And it seems to work--even people who don't buy into other core practices of XP seem to have adopted refactoring as a central element in their process.The catalog of refactorings that the books provides are a first class reference on how to clean up particular problems. But to me, the most valuable part of the book is its first fifty pages. Fowler starts the book with a simple, but ugly, example, that he proceeds to refactor, step-by-step, into something rather elegant. If you like to learn principles first, you might want to read the second chapter before going through the example, but I found it a very valuable exercise. I recommend coding the example in your language of choice, then refactoring along with Fowler as you work through the example.There is a temptation to relegate refactoring, like testing, to simply another development technique. But like testing, refactoring is at the core of a development philosophy: "I know I'm not going to get it right on my first pass, so I'll be satisfied with making it as right as I can. Having done that, I'll have a much better idea how to make it better, and I will. But time's a' wasting, so I need to get moving."This philosophy of continuous improvement allows the developer to get into action fairly quickly, and it reduces the risk of failure-by-delay. Fowler's book is a top-notch resource that will help the developer create more flexible code more quickly. I can recommend 'Refactoring' without reservation.

A little while back I was introduced to a word I had never heard before, Refactoring. I was told to get Martin Fowler's book and read it so I could gain a better understanding of what Refactoring was. Well folks, I would classify this book as a 'Hidden Treasure'. Although it is not a flashy or well known title, I believe its impact can be much deeper and long lasting than many of the mainstream, more popular technology books. The underlying theories that it teaches can be applied for years, even when languages change.There are only a couple of things I would change about this book, which I will mention below. PrefaceThe Preface it brief enough, and gives the definition for the word Refactoring. This is a good thing because right form the start you get the true definition of Refactoring. In short, refactoring is the process of changing code to improve the internal structure, but not changing the external behavior.Chapter 1: Refactoring, a First ExampleIn this chapter Mr. Fowler tries to start by showing a simple Refactoring example. The problem is that the chapter then goes on for 50+ pages. Mr. Fowler explains his reasons for doing this, but I think that a simple example should have been much simpler. Especially when it is in the first chapter of the book. It's not that this isn't a good chapter. I feel it's just too soon in the book. I would have put it at the end.Chapter 2: Principles of RefactoringThis is an excellent chapter. The definition of Refactoring is discussed as well as the following questions: Why should you refactor? When should you refactor? What do I tell my manager? This last question may seem funny, but when you read this chapter you will understand why it is in there. This chapter also discusses common problems that occur during Refactoring, and Refactoring and performance. Chapter 3: Bad Smells in CodeIn this chapter things that cause code to 'smell' are discussed. When code 'smells' it could be an indicator that refactoring is needed. 22 different 'smells' are discussed. My favorites were Duplicated Code, Large Class, and Lazy Class. This is a chapter full of awesome hints.Chapter 4: Building TestsBuilding tests is an important part refactoring. Refactoring is done in small steps, and after every step you should test. In this chapter the discussion covers the processes and methodology of applying tests during refactoring.Chapter 5: Toward a Catalog of RefactoringsThis chapter is a quick setup for chapters 6 to 12. Mr. Fowler explains his method for cataloging the individual refactorings. What is pretty amazing is that he has taken a lot of time naming and detailing each refactoring.Chapter 6: Composing MethodsOne of my favorite chapters. Mr. Fowler opens by saying, "A large part of my refactoring is composing methods to package code properly." This chapter is all about that. 9 total refactorings are explained. My favorite ones are Inline Method and Extract Method.Chapter 7: Moving Features Between ObjectsSometimes you need

One can read good books on a specific technology (COM, UML etc) or on specific programming languages or even on different approaches to software development (RUP, OPEN etc) but every now and then a true classic comes along. Like Design Patterns 4 years ago now refactoring comes along. Every serious OO developer should own both of these books. Get your hands on Refactoring if only to read chapter 3, which summarises all the 'bad smells' that may creep into code. 21 generic examples of what is bad programming and why. The remainder of the book describes numerous techniques (refactorings) for changing existing code in order to remove the 'smell'. Most refactorings are accompanied with some UML, which should be enough to get the idea, and they are then further described in Java. What makes this great a book is that it can be used as a reference very easily since its design was well thought out for this purpose with a comprehensive index and tables matching smells and respective refactorings. If any of this rings a bell to CODE COMPLETE readers it should cause the ideas are very similar but very much updated here. Fowler's writing style makes once again for easy, pleasant reading. Unreservedly recommended.

I spent seven years in the Smalltalk environment figuring (parts) of this stuff out for myself. You don't have to - buy Martin's book and shave at least a few years off the learning curve. Refactoring is an indispensable part of software development. Like it or not, whatever you write today will be "wrong" sometime in the future. You need to have techniques for transitioning to the "right" stuff. Refactoring provides you with a wealth of small tools that can make the transition easier. Not only that, having confidence that you can refactor your code later (supported by relentless testing) actually relieves some of the pressure you feel when you write the code the first time. Get it working, then get it right. Don't panic. Don't sweat. Enjoy your work like you did when you started (remember?). Let Refactoring guide the way.A practical guide for any OO developer, no matter what language you are working in, though you need enough familiarity with Java to read the examples.

It's a rare book that causes the reader to say: "This changes *everything*." The Design Patterns book is one such, Refactoring is another. The introductory chapters establish a clear theoretical and practical basis for the catalog of refactorings that make up the larger part of the text. Many of the examples are trivial, but then, many of the refactorings occur in simple situations. The more complex refactorings are usually accompanied by detailed example code. The mechanics section in each refactoring is an outstanding tool, and I expect to use it quite frequently.I have followed the 'extreme programming' (XP) movement for some time, and I'm an ardent fan, as is, so I gather, Fowler himself. But don't be fooled by this: the book is not just for the XP crowd. All programmers who use Java (or have used more than one other oo language), will find this book a huge resource. I have a library that I recommend to journey-folk who aspire to mastery. Refactoring is certainly the newest addition. I think this book will be an instant classic.I cannot say enough. Why not buy it now?