Introduction

When and how to use enums in Swift? This is a detailed practical overview of all the possibilities enums can offer you.

Similarly to the switch statement, enum's in Swift may at first glance look like a slightly improved variant of the well known C enum statement. I.e. a type that allows you to define that something is "one of something more general". However, the particular design decisions behind Swift's enums allow it to be used in a much wider range of practical scenarios than plain C enums. In particular, they're great tools to clearly manifest the intentions of your code.

In this post, we'll first look at the syntax and possibilities of using enum, and will then use them in a variety of (hopefully) practical, real world scenarios to give a better idea of how and when to use them. We'll also look a bit at how enums are being used in the Swift Standard library.

Before we dive in, here's a definition of what enums can be. We'll revisit this definition later on:

"Enums declare types with finite sets of possible states and accompanying values. With nesting, methods, associated values, and pattern matching, however, enums can define any hierarchically organized data."

First, though, what are enums?