Transcript

One of the most fundamental principles you'll see over and over again in software engineering literature and writing clean, maintainable code is the DRY principle. DRY stands for Don't Repeat Yourself, and the idea behind it is pretty straightforward. Every piece of knowledge or logic in your system should ideally have a single source of truth. You shouldn't find yourself copying and pasting the same logic, business rules, or code blocks in multiple places. If you do, you're violating the DRY principle. Take e-mail validation logic, for example. That logic should live in a single place and be imported. The parts of the application that needs it, your registration form, your checkout page, your profile settings, they should all reference from the same source of truth. The moment you start duplicating logic across your code base, you create a maintenance problem. If the validation rules ever need to change, you now have to track down every single place you copy that code and update all of them. And if you miss 1, you now have a bug when DRY is applied. Well, a change to any single piece of logic doesn't require you to hunt down and update unrelated parts of your code base. And for the parts of the application that are logically. Stated they stay In Sync automatically because they all point to the same source of truth. DRY also shows U in other levels of software design. Database abstraction tools like Hibernate follow DRY by letting you define your data model once and reuse it across queries rather than rewriting table structures everywhere. For configuration management, Environment variables let you define a parameter in one place instead of scattering it across your entire code base. That said, like every engineering principle, DRY is not a one-size-fits-all. DRY applies to duplicating knowledge and intent, not just lines. Code 2 functions can look nearly identical and still be completely fine to keep separate because they represent different concepts that just happen to look similar. For example, take a shipping address validator and a billing address validator. Forcing them into one shared function couples 2 functions that have no business being coupled, and when one of them needs to change, you're now untangling a mess you didn't need to create in the 1st place. The real goal of DRY isn't to eliminate every duplicate line of code, it's to reduce unnecessary repetitions while keeping your system readable, maintainable, and easy to reason about. The keyword there is unnecessary, and knowing the difference is what separates applying a principle from blindly following one. Follow my codes for more programming videos like this and check out amacom for more.