My biggest takeaways while learning and now preferring FP that have changed my perspective on OOP languages is the following (some of them are not good):
- Quarantine side effects. This has help a lot with reducing bugs and making unit testing easier since it means that my pure functions aren’t intermingled with all of the effectful code.
- It made me realize how much harder OOP is to get the same result. Mutability adds complexity that most of us don’t even notice: Time. When a value changes over time you pretty much have to us a debugger to see it change and why it’s changing. In FP it’s just a new binding. Also, coupling behavior with data makes it even harder to manage because you end up with temporal coupling when one property or method changes a value and a method was depending on the value of a member var to be in a certain state. In FP, new state changes are very explicit (and far simpler). State (data) goes in… and new state comes out.
- The bad part is that FP has made me realize that is so much simpler to program in so I get annoyed in OOP languages when I have to do something simple like create a class just to add behavior to my program when a simple function will do.