Swift enum both a string and an int

Question

I have a situation where I'm trying to do binary decoding of some data and the data types have both a numerical value and a string value and a name. I was thinking of using an enum such as:

enum TARGET_TRACK_TYPE : String {
    case TT_INVALID          = "Invalid"
    case TT_TRUE_TRACK_ANGLE = "True Track Angle"
    case TT_MAGNETIC         = "Magnetic"
    case TT_TRUE             = "True"
}

However I also know that:

TT_INVALID = 0 and TT_TRUE_TRACK_ANGLE = 1, etc. Is there an easy way to encapsulate both these "things" the string and the numerical value into an enum construct or do i need to make some sort of struct/class to handle this?

I guess I'd like to do something like

let a = TARGET_TRACK_TYPE.rawValue(value: 2) println(a)

which would print True Track Angle

Again, I know this can be done with a struct or a class but I'm specifically interested in the enum

Or for another example:

/// Emitter Category is defined in section 3.5.1.10 of the GDL90 Spec
struct EmitterCategory {

let category : Int

func getString() -> String {

    switch(category) {
    case 0:
        return "No aircraft type information";
    case 1:
        return "Light";
    case 2:
        return "Smalle";
    case 3:
        return "Large";
    case 4:
        return "High Vortex Large";
    case 5:
        return "Heavy";
    case 6:
        return "Highly Manuverable";
    case 7:
        return "Rotorcraft";
    case 8:
        return "(Unassigned)";
    case 9:
        return "Glider/sailplane";
    case 10:
        return "Ligther than air";
    case 11:
        return "Parachutist/sky diver";
    case 12:
        return "Ultra light/hang glider/paraglider";
    case 13:
        return "(Unassigned)";
    case 14:
        return "Unmanned aerial vehicle";
    case 15:
        return "Space/transatmospheric vehicle";
    case 16:
        return "(Unassigned)";
    case 17:
        return "Surface vehicle - emergency vehicle";
    case 18:
        return "Surface vehicle - service vehicle";
    case 19:
        return "Point obstacle";
    case 20:
        return "Cluster Obstacle";
    case 21:
        return "Line Obstacle";
    default:
        return "(reserved)";
    }
}
}

Is there a way to refactor this struct into an enum such that I construct the enum with an integer value but I "read" the enum as a string? I'm pretty sure the answer is no.

Answer 1

These answers have one thing missing i.e. How to create enum instance from String value. We can create a custom initializer for it as follows:

enum Gender: Int, CustomStringConvertible {
        case other = 0
        case male
        case female
        
        var description: String {
            switch self {
            case .other:
                return "Other"
            case .male:
                return "Male"
            case .female:
                return "Female"
            }
        }
        
        static func initialize(stringValue: String)-> Gender? {
            switch stringValue {
            case Gender.other.description:
                return Gender.other
            case Gender.male.description:
                return Gender.male
            case Gender.female.description:
                return Gender.female
            default:
                return nil
            }
        }
    }

Answer 2

Summing up @Jeef's answer and @NobodyNada's comment, here's a solution

public enum Animal: Int, CustomStringConvertible {
    case Dog, Cat

    public var description: String {
        switch self.rawValue {
        case 0: return "Dog"
        case 1: return "Cat"
        default: return ""
        }
    }
}

var animal = Animal.Dog
print(animal) // Dog

Answer 3

You should use RawRepresentable

@objc enum AppEvent:Int, RawRepresentable  {
    case appLaunch
    case homeScreen

    public typealias RawValue = String

    public var rawValue: RawValue {
        switch self {
        case .appLaunch                      : return "appLaunch"
        case .homeScreen                    : return "homeScreen"
    }

    public init?(rawValue: RawValue) {
        switch rawValue {
        case "appLaunch"                    : self = .appLaunch
        case "homeScreen"                   : self = .homeScreen 
    }

Answer 4

With Swift 4.2 this can be done using CaseIterable. One, relatively concise way is to do the following

enum Directions: String, CaseIterable {
    case north, south, east, west

    static var asArray: [Directions] {return self.allCases}

    func asInt() -> Int {
        return Directions.asArray.firstIndex(of: self)!
    }
}

print(Directions.asArray[2])
// prints "east\n"

print(Directions.east.asInt())
// prints "2\n"

print(Directions.east.rawValue)
// prints "east\n"

Answer 5

Have you considered using a dictionary?

 let targetTrackDict: [Int: String] =
      [99: "Invalid",
       1: "True Track Angle",
       2: "Magnetic",
       5: "True"]

Note the number codes don't have to be ordered or contiguous. Being specific about the dictionary's type in its declaration prevents a lot of warnings or errors in the following snippets.

Getting the name for a code is easy:

var code = 2
if let name = targetTrackDict[code] {
  print("\(name) has code \(code)")
} else {
  print("\(code) is not a valid track type")
}

I haven't found a tidy way of getting the code for a name, but this does it:

let magneticCode = targetTrackDict.first(where: 
    {key, value in value == "Magnetic"})?.key
// returns an optional

and you would of course dress it up as a function. What you don't get automatically is an internal name for your track type, but do you need one? And the line above does it for you in a way.

Answer 6

I think this will do it for me. Thank you self.. :)

protocol GDL90_Enum  {
      var description: String { get }
}

enum TARGET_ADDRESS_TYPE : Int, GDL90_Enum {
   case ADSB_ICAO_ADDRESS = 0
   case ADSB_SELF_ADDRESS = 1
   case TISB_ICAO = 2
   case TISB_TRACK_ID = 3
   case SURFACE_VEHICLE = 4
   case GROUND_STATION = 5

   var description: String {
      switch self {
   case .ADSB_ICAO_ADDRESS:
      return "ADS-B with ICAO address"
   case .ADSB_SELF_ADDRESS:
      return "ADS-B with Self-assigned address"
   case .TISB_ICAO:
      return "TIS-B with ICAO address"
   case .TISB_TRACK_ID:
         return "TIS-B with track file ID"
   case .SURFACE_VEHICLE:
         return "Surface Vehicle"
   case .GROUND_STATION:
         return "Ground Station Beacon"
   default:
         return "Reserved"
      }
   }
}