When learning a new programming language, you're not just learning syntax, built-in libraries, tooling, terminology, formatting style, and so on. There is also a somewhat vaguely defined idea of what constitutes good code, a way of performing some tasks that fits well with the language and has evolved together with it over time. In Swift, such code is often referred to as Swifty code. This is in no way a well-defined term, and experts in the language may disagree on some points. Here, we will only cover things where there seems to be a consensus. The list is by no means exhaustive, and there are exceptions to many of these.

Many of these points are covered in Apple's official guidelines (https://swift.org/documentation/api-design-guidelines/). We strongly recommend reading it; it's a fairly short page and a very easy read.