Access String value in enum without using rawValue

While I didn’t find a way to do this using the desired syntax with enums, this is possible using structs.

struct DatabaseKeys {

    struct User {
        static let identifier = "User"
        static let Username = "username"
    }

}

To use:

myUser[DatabaseKeys.User.Username] = "Johnny"

Apple uses structs like this for storyboard and row type identifiers in the WatchKit templates.