Type safe text keys for localizable strings files

TextKey.swift

protocol LocalizedText {
    func asLocalizedText() -> String
}

protocol TextKey : LocalizedText {
    var key: String { get }
}

extension TextKey {
    func asLocalizedText() -> String {
        return Bundle.main.localizedString(forKey: key, value: nil, table: nil)
    }
}

protocol TextKeyEnum : TextKey {
    associatedtype T : RawRepresentable where T == Self, T.RawValue == String
}

extension TextKeyEnum {
    typealias T = Self
    var key: String { get { self.rawValue } }
}

enum Text {
    enum Common : String, TextKeyEnum {
        case ok = "text.common.ok"
    }
}