How to display OptionSet values in human-readable form?

Question

Swift has the OptionSet type, which basically adds set operations to C-Style bit flags. Apple is using them pretty extensively in their frameworks. Examples include the options

Answer 1

Here is one approach I've taken, using a dictionary and iterating over the keys. Not great, but it works.

struct MyOptionSet: OptionSet, Hashable, CustomStringConvertible {

    let rawValue: Int
    static let zero = MyOptionSet(rawValue: 1 << 0)
    static let one = MyOptionSet(rawValue: 1 << 1)
    static let two = MyOptionSet(rawValue: 1 << 2)
    static let three = MyOptionSet(rawValue: 1 << 3)

    var hashValue: Int {
        return self.rawValue
    }

    static var debugDescriptions: [MyOptionSet:String] = {
        var descriptions = [MyOptionSet:String]()
        descriptions[.zero] = "zero"
        descriptions[.one] = "one"
        descriptions[.two] = "two"
        descriptions[.three] = "three"
        return descriptions
    }()

    public var description: String {
        var result = [String]()
        for key in MyOptionSet.debugDescriptions.keys {
            guard self.contains(key),
                let description = MyOptionSet.debugDescriptions[key]
                else { continue }
            result.append(description)
        }
        return "MyOptionSet(rawValue: \(self.rawValue)) \(result)"
    }

}

let myOptionSet = MyOptionSet([.zero, .one, .two])

// prints MyOptionSet(rawValue: 7) ["two", "one", "zero"]