Extendable 'enums' using RawRepresentable

RawRepresentableConstants.swift

import Foundation

/*
 This is used by NSNotification.Name to allow enum-like members,
 but where new members can be added in an extension!
 
 enum Directions: String {
 case north = "North"
 }
 
 extension Directions {
 case south = "South" <-- This is not allowed by the compiler
 }
 
 */

struct Direction: RawRepresentable {
    typealias RawValue = String
    var rawValue: String
    
    init(_ rawValue: RawValue) {
        self.rawValue = rawValue
    }
    
    init?(rawValue: RawValue) {
        self.rawValue = rawValue
    }
    
}

extension Direction {
    static let North = Direction("North")
    static let South = Direction("South")
}

extension Direction {
    static let East = Direction("East")
    static let West = Direction("West")
}

func display(_ value: Direction) {
    print("\(value.rawValue)")
    
}

display(.West) // output: West

// The enum-like syntax above works because the parameter type contains a member of that type
// This can be leveraged as follows:

struct Thing {
    let name: String
    static let Thing1 = Thing(name: "Thing1")
    static let Thing2 = Thing(name: "Thing2")
}

func display(_ value: Thing) {
    print("\(value.name)")
    
}

display(.Thing1)  // output: Thing1