How to make a Swift String enum available in Objective-C?

I have this enum with String values, which will be used to tell an API method that logs to a server what kind of serverity a message has. I'm using Swift 1.2, so enums can be mapped to Objective-C

@objc enum LogSeverity : String {
    case Debug = "DEBUG"
    case Info = "INFO"
    case Warn = "WARN"
    case Error = "ERROR"
}

I get the error

@objc enum raw type String is not an integer type

I haven't managed to find anywhere which says that only integers can be translated to Objective-C from Swift. Is this the case? If so, does anyone have any best-practice suggestion on how to make something like this available in Objective-C?

One of the solutions is to use the RawRepresentable protocol.

It's not ideal to have to write the init and rawValue methods but that allows you to use this enum as usual in both Swift and Objective-C.

@objc public enum LogSeverity: Int, RawRepresentable {
    case debug
    case info
    case warn
    case error

    public typealias RawValue = String

    public var rawValue: RawValue {
        switch self {
            case .debug:
                return "DEBUG"
            case .info:
                return "INFO"
            case .warn:
                return "WARN"
            case .error:
                return "ERROR"
        }
    }

    public init?(rawValue: RawValue) {
        switch rawValue {
            case "DEBUG":
                self = .debug
            case "INFO":
                self = .info
            case "WARN":
                self = .warn
            case "ERROR":
                self = .error
            default:
                return nil
        }
    }
}

From the Xcode 6.3 release notes (emphasis added):

Swift Language Enhancements

...
Swift enums can now be exported to Objective-C using the @objc attribute. @objc enums must declare an integer raw type, and cannot be generic or use associated values. Because Objective-C enums are not namespaced, enum cases are imported into Objective-C as the concatenation of the enum name and case name.

Here's a solution that works.

@objc public enum ConnectivityStatus: Int {
    case Wifi
    case Mobile
    case Ethernet
    case Off

    func name() -> String {
        switch self {
        case .Wifi: return "wifi"
        case .Mobile: return "mobile"
        case .Ethernet: return "ethernet"
        case .Off: return "off"
        }
    }
}

Here is work around if you really want to achieve the goal. However, you can access the enum values in objects that Objective C accepts, not as actual enum values.

enum LogSeverity : String {

    case Debug = "DEBUG"
    case Info = "INFO"
    case Warn = "WARN"
    case Error = "ERROR"

    private func string() -> String {
        return self.rawValue
    }
}

@objc
class LogSeverityBridge: NSObject {

    class func Debug() -> NSString {
        return LogSeverity.Debug.string()
    }

    class func Info() -> NSString {
        return LogSeverity.Info.string()
    }

    class func Warn() -> NSString {
        return LogSeverity.Warn.string()
    }

    class func Error() -> NSString {
        return LogSeverity.Error.string()
    }
}

To call :

NSString *debugRawValue = [LogSeverityBridge Debug]