I am a big fan of Protocol-oriented development. It allows you to do component-style programming, where it's very simple (swifty) to extend functionality onto struct/classes in a easy to understand, reusable way.

Additionally, language features like guard/optionals/etc... allow you to deal with error states & control flow easily.

Two good videos I'd recommend on protocol-oriented development:

Protocol-oriented programming in swift (part 1): https://developer.apple.com/videos/play/wwdc2015/408/

Protocol and value-oriented programming in UIKit apps (part 2): https://developer.apple.com/videos/play/wwdc2016/419