Testing for enum value fails if one has associated value?

Question

I\'m testing this in the Playground and I\'m not sure how to do this. With a normal enum that doesn\'t have associated values, everything is fine.

enum Compa         


        

Answer 1

Enumerations are automatically Equatable when they have a raw value that's Equatable. In your first case, the raw value is assumed to be Int, but it would work if you'd given it another specific type like UInt32 or even String.

Once you add an associated value, however, this automatic conformance with Equatable doesn't happen any more, since you can declare this:

let littleNorth = CompassPoint.North(2)
let bigNorth = CompassPoint.North(99999)

Are those equal? How should Swift know? You have to tell it, by declaring the enum as Equatable and then implementing the == operator:

enum CompassPoint : Equatable {
    case North(Int)
    case South
    case East
    case West
}

public func ==(lhs:CompassPoint, rhs:CompassPoint) -> Bool {
    switch (lhs, rhs) {
    case (.North(let lhsNum), .North(let rhsNum)):
        return lhsNum == rhsNum
    case (.South, .South): return true
    case (.East, .East): return true
    case (.West, .West): return true
    default: return false
    }
}

Now you can test for equality or inequality, like this:

let otherNorth = CompassPoint.North(2)
println(littleNorth == bigNorth)            // false
println(littleNorth == otherNorth)          // true