The DRY Design Principle

In this week’s blog post, I will be discussing some of what I learned about the DRY design principle from the article “The DRY Principle: Benefits and Costs with Examples” written by The Valuable Dev. I initially chose this particular article because it perfectly aligns with the DRY design principle topic within the syllabus. This article discusses what DRY is, as well as why you shouldn’t always use DRY. I personally found the author’s use of humor to be very refreshing. I feel many of the blogs I have read so far have seemed to be robotic in how they are written.

The article says that DRY is primarily about a repetition of knowledge first and foremost. “Therefore, the logic of this shipment should only appear once in the application. Why? Imagine that you need to send shipments to a warehouse. You need to trigger this behavior in 76 different places in your application. No problem: you repeat the logic 76 times. After a while, your boss comes to you and asks you to change this behavior. Instead of sending shipments to one warehouse, you need to send them to three different ones. The result? You’ll spend a lot of time on your shipment logic since you’ll have to change it in 76 different places! This is a waste of time and a good way to produce bugs to piss your boss off.” The author suggests instead of repeating the logic that you are using, and it would be better to use abstraction to prevent the kind of issues that the example given causes. This would not only allow for changes to be made faster but also minimize the risk of bugs being created because you are only changing code in one area instead of 76 different places.

The author also discusses a situation where DRY doesn’t apply. In this example, the author is working on software for a VOD (video on demand) platform that both filmmakers and content teams would use regularly. The author was considering creating abstract classes to use instead of the current implementation that was being used due to many classes being almost copy-pasted, as well as seemingly having similar utility for both filmmakers and content teams. “In many cases, we knew that the interface would evolve differently in the future. We would have created a lot of conditionals in the controllers’ actions if we had created one set of controllers for both applications. Nobody wants a forest of if statements; the resulting code would have been way more complex. Additionally, the controllers shouldn’t contain any business logic. If you recall the definition of the DRY principle, it’s this knowledge and business logic that should not be duplicated.” As both classes would become more developed in the future, they would differ significantly. If they were made into an abstraction, the code needed for them to work for filmmakers and content creators would have been messy and complicated to manage.

Article: https://thevaluable.dev/dry-principle-cost-benefit-example/