Get associated value from enumeration without switch/case

Question

I\'ve got an enumeration with a few different cases which are different types, e.g.

enum X {
    case AsInt(Int)
    case AsDouble(Double)
}

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Answer 1

As of Swift 2 (Xcode 7) this is possible with if/case and pattern matching:

let x : X = ...
if case let .AsInt(num) = x {
    print(num)
}

The scope of num is restricted to the if-statement.

Answer 2

There are actually multiple ways to do it.

Let's do it by extending your enum with a computed property:

enum X {
    case asInt(Int)
    case asDouble(Double)

    var asInt: Int? {
        // ... see below
    }
}

Solutions with if case

By having let outside:

var asInt: Int? {
    if case let .asInt(value) = self {
        return value
    }
    return nil
}

By having let inside:

var asInt: Int? {
    if case .asInt(let value) = self {
        return value
    }
    return nil
}

Solutions with guard case

By having let outside:

var asInt: Int? {
    guard case let .asInt(value) = self else {
        return nil
    }
    return value
}

By having let inside:

var asInt: Int? {
    guard case .asInt(let value) = self else {
        return nil
    }
    return value
}

The last one is my personal favorite syntax of the four solutions.