Hi OOPer, thanks so much for your reply. That was my first look at the problem, however when changing the argument label I was getting errors in the function code that the parameter name isn't correspond with the label in the function definition. You're absolutely right that they should operate and behave separately, however the code didn't seem to behave as if that were the case! Does my explanation above immediately make you think I'm doing something else that's obviously wrong for the code to behave in that way?

Thanks so much for the Stanford YouTube playlist and the Hacking With Swift site recommendations. They look like brilliant places to start! After a turbulent 2020, I've decided to retrain as a developer for Apple platforms - to build more future proof skills. I'm starting with the Develop in Swift iBook series Apple published earlier this year to give me a jump start then I'll move in to more involved content like this. Hello 👋 to everyone on the forums and looking forward to being a part of the developer community!