Enum backed with Int and String

IntAndString.swift

import Foundation

protocol IntAndString: RawRepresentable where RawValue == (Int, String)
{
  static var invalidInt: Int { get }
  static var invalidString: String { get }
}

extension IntAndString
{
  var int: Int { return self.rawValue.0 }
  var string: String { return self.rawValue.1 }
  
  static var invalidInt: Int { return -1 }
  static var invalidString: String { return "" }

  init?(int: Int) { self.init(rawValue: (int, Self.invalidString)) }
  init?(string: String) { self.init(rawValue: (Self.invalidInt, string)) }
}

extension IntAndString where Self: CaseIterable
{
  init?(rawValue: (Int, String))
  {
    if let match = Self.allCases.first(where: { $0.rawValue.0 == rawValue.0 || $0.rawValue.1 == rawValue.1 }) {
      self = match
    }
    else {
      return nil
    }
  }
}


enum Numbering: CaseIterable
{
  case first
  case second
}

extension Numbering: IntAndString
{
  var rawValue: (Int, String)
  {
    switch self {
      case .first: return (1, "first")
      case .second: return (2, "second")
    }
  }
}

let a = Numbering(int: 2)
let b = Numbering(string: "first")