Extensible enum raw values

extensible-raw-values.swift

import Foundation

struct X: Equatable, ExpressibleByStringLiteral {
    let strings: Set<String>

    init?(_ characters: String.CharacterView) {
        let strings = Set<String>(String(characters).components(separatedBy: ",").map{ String($0) })
        if strings.isEmpty {
            return nil
        }        
        self.strings = strings
    }

    init(stringLiteral value: String) {
        self.init(value.characters)!
    }

    init(extendedGraphemeClusterLiteral value: String) {
        self.init(stringLiteral: value)
    }

    init(unicodeScalarLiteral value: String) {
        self.init(stringLiteral: value)
    }
}
func ==(lhs: X, rhs: X) -> Bool {
    return lhs.strings == rhs.strings
}

enum E: X {
case fooBar = "foo-bar,f"
}

print(E.fooBar.rawValue)