What you describe is called the Expression Problem [1] in programming language design and there is no simple formulaic answer on which method is better. I think

What you describe is called the Expression Problem [1] in programming language design and there is no simple formulaic answer on which method is better. I think you have to consider many aspects of your code's current design and possible future evolution when deciding which approach to use. For example: do you expect to have more types of transforms, or more operations/method per type of transform? It also means you can't nitpick a limited tutorial for focusing on one approach vs. the other. Fortunately swift (as well as Rust or Kotlin) has excellent modern toolbox that includes protocol conformance and algebraic data types so you can use either one. Keep in mind that swift protocols avoid many of the pitfalls of Java\C++ school of OOP design you might have seen before that can only express "is-a" relationships. [1] https://en.wikipedia.org/wiki/Expression_problem https://en.wikipedia.org/wiki/Expression_problem