DRY and Once And Only Once isn’t about slavishly identifying similar code blocks. It’s about trying to arrange your code so that a single idea is expressed in a

DRY and Once And Only Once isn’t about slavishly identifying similar code blocks. It’s about trying to arrange your code so that a single idea is expressed in a single place. The initial API here is actually quite nice - there’s a good separation of abstraction and specification, and I can see all the information about an individual pizza in one place. The idea of making a pizza and the recipe for each pizza exist once in their respective places. It’s true that a common pitfall is to prematurely create abstractions before having concrete examples of how they’d be used. But DRY is a _refactoring_. It’s something you do to an existing codebase to better clarify its design, not necessarily something to strive for ahead of time. Much better to extract abstractions from existing examples. I always remember the tale Ron Jeffries tells of Kent Beck actually _introducing_ duplication to allow both pieces of code to be refactored. Duplication can be an opportunity to refactor towards a clearer design, but it’s not a mechanistic thing to do without thinking.