Non-contiguous raw value enumerations

Brennan Stehling recently uncovered a fantastic Swift feature I was completely unaware of. I knew you could create raw value enumerations that automatically incremented the value for each case:

enum MyEnumeration: Int {
   case one = 1, two, three, four
}

MyEnumeration.three.rawValue // 3

And I knew you could create raw value enumerations with hand-set values:

enum MyEnumeration: Int {
    case one = 1, three = 3, five = 5
}

But I didn’t know that you could mix and match the two in the same declaration! (Although, you probably shouldn’t do this for standards-based values like the following example…)

enum HTTPStatusCode: Int {
    // 100 Informational
    case continue = 100
    case switchingProtocols
    case processing
    // 200 Success
    case OK = 200
    case created
    case accepted
    case nonAuthoritativeInformation
}

HTTPStatusCode.accepted.rawValue // 202

How cool is that?

I’d probably reserve this approach for values with offsets (for example, “start at 1”), and where the underlying values don’t have established semantics. As Kristina Thai points out, skipping meaningful values doesn’t help readability or inspection.

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