Comment by jsbg
9 months ago
DRY is about ensuring that the same code doesn't have to change in two places because the engineer changing it in one place might not know that. But so many applications of DRY mindlessly violate the single responsibility principle and create coupling where there shouldn't be.
I always understood that the main reason for DRY is to ensure that the same business logic is managed only once in the codebase. I don't really care about having four similar functions for reading a file from disk, but I definitely wouldn't want multiple UserDiscountCalculator class implementations scattered all over the codebase.