AgileAttitudes Article
 
 
 

Vol 02 Issue 01- Eliminating code duplication

  
 
Back to the list of articles Agile Attitudes Volume 2, Issue 1 Jan. 11, 2005 A free bi-weekly email newsletter Brought to you by Agile Rules consulting www.agilerules.com ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Welcome to Agile Attitudes, a newsletter of ideas, insights and technical tips that help people find better ways to develop software. Feel free to share this with anyone - just be sure you send or print the whole thing, including the copyright notice. Directions for managing your subscription are below. O><O><O><O><O><O Eliminating code duplication by David Kramer There are many "best practices" (golden rules) of software development. Some don't make much sense, and some we follow without really knowing why, but some practices offer so many reasons to follow them, that you wonder why anyone even needs to be reminded of them. Eliminating code duplication falls into that last category for most developers, but it still pays to talk about why it's a good thing, and why it doesn't always happen. Why eliminate [nearly] duplicate code? - Code duplication means more code. More code means more time and more opportunities for bugs and other forms of "unintended functionality". More code is also harder to read later and harder to expand on. - If you write code to do essentially the same thing in more than one place, and you later need to change that code, you must remember all the places it was implemented. - Even if you don't need to modify the different code segments later, slight differences in implementation in each code segment can make your program work in unpredictable, inconsistent ways. - Writing code once helps encapsulate functionality. This is beneficial whether you're using an object-oriented language or not. - If you have just one code segment to implement a particular piece of functionality, it becomes much easier to share with other applications, or other parts of the same application. That, again, means less code you have to write. - Other developers trying to understand the code later will be puzzled over how the code segments are supposed to differ, which would be a natural conclusion. Why doesn't it always happen? - Insufficient planning: You may not have realized when you wrote function A that function B will need the same functionality. - Insufficient refactoring: Having discovered that function A and function B need the same functionality, you may not do anything about it. Most times, this is "penny-wise, pound-foolish" behavior. You may get this rev of your software out the door sooner, but tracking down the duplicated functionality later when it rears its head as a bug will be much harder. - Insufficient communication between developers. - Insufficient support from management. Some companies don't have the vision to let developers spend enough time refactoring instead of adding functionality. But there is a defense: cold, hard numbers. If you track the root cause of bugs, and can show how many might have been caught through this kind of refactoring, they will see the light. How do you eliminate code duplication? - Take the time to reflect on your codebase every now and then. If you don't get support from management, explain the advantages of fixing potential bugs while the code is fresh in your mind, catching more bugs before they're deployed, and making further enhancements easier to implement. - Write your software in clearly-defined layers, preferably either infrastructure-first, or working towards the middle. When you do this, you will see the places you can share code. If you write your code from the UI-down, you won't find the infrastructure elements that need to be shared, and you risk creating bugs in the infrastructure, where they're hardest to find. I hope I've been able to help you see the value of eliminating code duplication, and getting others to join the effort. Better code is almost always worth it in the end. O><O><O><O><O><O More articles on Agile software topics at http://www.agilerules.com Within our company we have a sub-specialty in embedded systems. Our site has articles on embedded XP and we support a discussion list focused on the use of agile methods for building embedded software. The list signup info is at http://www.agilerules.com/mailinglists.phtml O><O><O><O><O><O To help you get started with in-depth research into Agile Attitudes topics, we have added a Library section to our web site at http://www.agilerules.com/library.phtml Order using our links and receive discounts up to 30%! O><O><O><O><O><O If you enjoyed this issue or found it useful, forward it to a friend! Help spread the word about better ways to build software. Invite your friends and colleagues to join our growing reader community at http://www.agilerules.com/mailinglists.phtml O><O><O><O><O><O Looking for a speaker for your next corporate or society meeting? We present dynamic, informative programs on topics of interest to managers and technical staff in their transition to more flexible, robust ways to create software. 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