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This week in Coding Kitchen, we explore one of the key principles of Extreme Programming, YAGNI (You Ain’t Gonna Need It). This principle states that some capability we think our software will need in the future should not be built now because “you aren’t gonna need it“, or as XP co-founder Ron Jeffries put it, “Always implement things when you actually need them, never when you just foresee that you need them.

The YAGNI principle is to be used in conjunction with other practices, such as continuous integration, continuous refactoring and continuous automated unit testing. Without the additional use of any of these other practices, your code could go into Technical Debt, which means it could become disorganized and need to be reworked. Using the YAGNI principle saves you time by helping you to avoid writing code that you do not end up needing and by making your code better because you did not have to fill it with guesses that turned out to be wrong.

In an article posted by Martin Fowler, he uses an example about selling insurance for the shipping business. His example states that an insurance company’s software system is broken into two components, pricing and sales and that the dependencies cannot usefully build sales software until the relevant pricing software is completed. His example also states that while the company works on updating the pricing component to add support for risks from storms, they consider working on a feature they will not need for another six months for piracy pricing. By adding on this additional feature now, Fowler declares that doing so would incur three classes of presumptive features, and four kinds of costs that occur by neglecting YAGNI for them.

1) Wrong feature — Cost of building, cost of carry + cost of delay
2) Right feature, built wrong — Cost of repair, cost of carry + cost of delay
3) Right feature, built right — Cost of carry + cost of delay

I chose this article because this particular example given by Fowler highlights the benefits of using YAGNI and why neglecting to do so would inherently cause many issues and become costly. As a future software engineer, I would prefer having to write less code that is easier to understand rather than have lines of useless, possibly obsolete code. I found Fowlers explanation of YAGNI and his further explanation of the many ways applying this principle could cause problems in comparison to the very few ways it could be of benefit easy to understand and useful. Having knowledge of this principle as a programmer will make writing and editing code in my future professional endeavors much more time and cost effective.

Inspiration and information gathered for this blog post :




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