Getting All cases of Enum with Swift CaseIterable

In this article, we will learn how to get an array of all cased of Swift enum.

Enum is a data structure that let you define a group or related values.

This is very useful in many areas of iOS applications.

• You can use it to declare setting options, e.g., notification frequency.
• You can use it to define picker values.
• You can use it for your view model state, e.g., initial, loaded, loading.

For some use cases, you might want to get an array of all possible enum cases to present to users.

Getting All cases of an enum with Swift CaseIterable

To get an array of all enum cases, you make an enum conform to the CaseIterable protocol.

CaseIterable protocol will automatically provides a collection of enum cases which you can access via the allCases static property.

Here is an example where I use an enum to define an option for users to set how often they need to receive a notification.

enum NotificationFrequency: CaseIterable {
    case off
    case daily
    case weekly
    case monthly
}

By conforming to the CaseIterable protocol, we can access an array of all cases by using the .allCases static property.

print(NotificationFrequency.allCases.map { "\($0)" })
// ["off", "daily", "weekly", "monthly"]

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CaseIterable on Enum with Associated Values

CaseIterable will automatically synthesize allCases for enum case without associated value.

This makes sense because it is impossible for the compiler to know what you want for an associate value.

Here is an example of a GameConsole enum. Both cases have an associated value.

enum GameConsole: CaseIterable {
    case ps(Int)
    case xbox(String)
}

The compiler can't possibly produce a reasonable associated value for our enum.

If you try to conform an enum with an associated value with the CaseIterable protocol, you will get an error asking you to fulfill the CaseIterable requirement yourselves.

What you need to do is define static var allCases: [GameConsole] yourselves.

In this example, I list all possible associated enum values myself.

enum GameConsole: CaseIterable {
    static var allCases: [GameConsole] {
        return [
            .ps(1), .ps(1), .ps(3), .ps(4), .ps(5),
            .xbox(""), .xbox("360"), .xbox("one"), .xbox("Series X")
        ]
    }
    
    case ps(Int)
    case xbox(String)
}

Does not conform to protocol CaseIterable

Swift also can't synthesize allCases for an enum with a case marked with the @available attribute.

For example, I have a PlatformSpecificEnum enum with cases that are available based on a platform.

enum PlatformSpecificEnum: CaseIterable {
    static var allCases: [PlatformSpecificEnum] {
        #if os(iOS)
        return [.common, .notOnMac]
        #elseif os(macOS)
        return [.common, .notOniOS]
        #endif
    }
    
    case common
    
    @available(macOS, unavailable)
    case notOnMac
    
    @available(iOS, unavailable)
    case notOniOS
}

In this case, we need to define allCases ourselves.

I return all cases that are available on that particular platform.

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CaseIterable Order

By default, the order of he synthesized allCases is the same order as their declaration.

If you want to change the order, you can either:

• Change the order of the declaration.
• Implement your own static var allCases.

These two would produce the same order.

enum OrderEnum: CaseIterable {
    static var allCases: [OrderEnum] {
        return [c, b, a]
    }
    case a
    case b
    case c
}

And

enum OrderEnum: CaseIterable {
    case c
    case b
    case a
}