editing-failable-enums-with-optionals-5.swift

    enum SegueIdentifier: String {
        case ToRed = "Red"
        case ToGreen = "Green"
        case ToBlue = "Blue"
        
         init?(_ rawValue: String?) {
            let out = SegueIdentifier(rawValue: rawValue ?? "")
            if rawValue != nil && out != nil {
                self = out!
            } else {
                return nil
            }
        }
    }