97 Things Every Programmer Should Know

Chapter 6. Before You Refactor

Rajith Attapattu

AT SOME POINT, every programmer will need to refactor existing code. But before you do so, please think about the following, as this could save you and others a great deal of time (and pain):

• The best approach for restructuring starts by taking stock of the existing codebase and the tests written against that code. This will help you understand the strengths and weaknesses of the code as it currently stands, so you can ensure that you retain the strong points while avoiding the mistakes. We all think we can do better than the existing system…until we end up with something no better—or even worse—than the previous incarnation because we failed to learn from the existing system’s mistakes.

• Avoid the temptation to rewrite everything. It is best to reuse as much code as possible. No matter how ugly the code is, it has already been tested, reviewed, etc. Throwing away the old code—especially if it was in production—means that you are throwing away months (or years) of tested, battle-hardened code that may have had certain workarounds and bug fixes you aren’t aware of. If you don’t take this into account, the new code you write may end up showing the same mysterious bugs that were fixed in the old code. This will waste a lot of time, effort, and knowledge gained over the years.

• Many incremental changes are better than one massive ...