Seeing that Uncle Bob is making a new version of Clean Code I decided to try and find this article about the original.
Why is it a void method? This only tells me that some state is mutated somewhere, but the effect is neither visible nor documented.
I would expect a function called “calculate” to just return a number and not have any side effects.
You’re nitpicking.
As it happens, it’s just an example to illustrate specifically the “extract to method” issues the author had.
Of course, in a real world scenario we want to limit mutating state, so it’s likely this method would return a Commission list, which would then be used by a Use Case class which persists it.
I’m fairly sure the advice about limiting mutating state is also in the book, though.
At the same time, you’re likely going to have a void somewhere, because some use cases are only about mutatimg something (e.g. changing something in the database).
It’s not nitpicking, stuff like this is far more impactful than choosing between 5 lines vs 10 lines long methods, or whether the hasExtraCommissions “if” belongs inside or outside of calculateExtraCommissions. This kind of thing should immediately jump out at you as a red flag when you’re reading code, it’s not something to handwave away as a detail.
I never claimed it’s not important, I’m just saying it’s not relevant here, as there is no context to where this method was put in the code.
As I said, it might be top-level. You have to mutate state somewhere, because that’s what applications ultimately do. You just don’t want state mutations everywhere, because that makes bad code.
