Enum associated values

As well as storing a simple value, enums can also store associated values attached to each case. This lets you attach additional information to your enums so they can represent more nuanced data.

For example, we might define an enum that stores various kinds of activities:

enum Activity {
    case bored
    case running
    case talking
    case singing
}

That lets us say that someone is talking, but we don’t know what they are talking about, or we can know that someone is running, but we don’t know where they are running to.

Enum associated values let us add those additional details:

enum Activity {
    case bored
    case running(destination: String)
    case talking(topic: String)
    case singing(volume: Int)
}

Now we can be more precise – we can say that someone is talking about football:

let talking = Activity.talking(topic: "football")

SAVE 50% To celebrate Black Friday, all our books and bundles are half price, so you can take your Swift knowledge further without spending big! Get the Swift Power Pack to build your iOS career faster, get the Swift Platform Pack to builds apps for macOS, watchOS, and beyond, or get the Swift Plus Pack to learn advanced design patterns, testing skills, and more.

Save 50% on all our books and bundles!

Sponsor Hacking with Swift and reach the world's largest Swift community!