Swift enum all values

In this quick tutorial I'll show you how to get all the possible values for a Swift enum type with a generic solution written in Swift 4.

2017/10/12iOS

From Swift 4.2 you can simply conform to the CaseIterable protocol, and you'll get the allCases static property for free. If you are reading this blog post in 2020, you should definitely upgrade your Swift language version to the latest. 🎉🎉🎉

enum ABC: String, CaseIterable {
    case a, b, c
}

print(ABC.allCases.map { $0.rawValue })

If you are targeting below Swift 4.2, feel free to use the following method...


The EnumCollection protocol approach

First we need to define a new EnumCollection protocol, and then we'll make a protocol extension on it, so you don't have to write too much code at all.

public protocol EnumCollection: Hashable {
    static func cases() -> AnySequence<Self>
    static var allValues: [Self] { get }
}

public extension EnumCollection {

    public static func cases() -> AnySequence<Self> {
        return AnySequence { () -> AnyIterator<Self> in
            var raw = 0
            return AnyIterator {
                let current: Self = withUnsafePointer(to: &raw) { $0.withMemoryRebound(to: self, capacity: 1) { $0.pointee } }
                guard current.hashValue == raw else {
                    return nil
                }
                raw += 1
                return current
            }
        }
    }

    public static var allValues: [Self] {
        return Array(self.cases())
    }
}

From now on you only have to conform your enum types to the EnumCollection protocol and you can enjoy the brand new cases method and allValues property which will contain all the possible values for that given enumeration.

enum Weekdays: String, EnumCollection {
    case sunday, monday, tuesday, wednesday, thursday, friday, saturday
}

for weekday in Weekdays.cases() {
    print(weekday.rawValue)
}

print(Weekdays.allValues.map { $0.rawValue.capitalized })

Note that the base type of the enumeration needs to be Hashable, but that's not a big deal. However this solution feels like past tense, just like Swift 4, please consider upgrading your project to Swift 5. Thx, bye! 👋


External sources

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Tibor Bödecs

Creator of http://theswiftdev.com (weekly Swift articles), server side Swift enthusiast, full-time dad. -- Follow me & feel free to say hi. 🤘🏻 -- #iOSDev #SwiftLang

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