SwiftClassClusterProposal.swift

//: Playground - noun: a place where people can play

import Foundation

enum GameSystemIdentifier
{
    case Wii
    case Xbox
    case PlayStation
}

struct Game
{
    let name: String
    let URL: NSURL
    let gameSystemIdentifier: GameSystemIdentifier
}

// Abstract class
// Handles receiving a Game struct, and then can "play" the game
// Because each system is different, there are specialized subclasses intended to each handle a specific system
class GameSystem
{
    // This method is invoked whenever GameSystem(game: game) is called to determine what subclass should be initialized
    // The return type should (theoretically) be of type GameSystem.Type, but alas that is currently a compile-time error
    class func dynamicTypeForInitializationParameters(parameters: [String: AnyObject]) -> AnyObject.Type /* GameSystem.Type */
    {
        // The `parameters` dictionary maps strings representing the initializer parameter names to the provided values
        // In this case, "game" maps to an instance of Game
        guard let game = parameters["game"] as? Game else { return GameSystem.self }
        
        switch game.gameSystemIdentifier
        {
        case .Wii: return WiiGameSystem.self
        case .Xbox: return XboxGameSystem.self
        case .PlayStation: return PlaystationGameSystem.self
        }
    }
    
    init(game: Game)
    {
        // Initialize as normal
    }
}


// "Private" implementation subclasses, specialized for handling games made for that specific system
class WiiGameSystem { }
class XboxGameSystem { }
class PlaystationGameSystem { }


// In practice, the gameSystemIdentifier would be determined dynamically by reading the UTI of the file at URL
let game = Game(name: "Pokemon", URL: NSURL(string: "path/to/game")!, gameSystemIdentifier: .Wii)

// Caller has no need to know exactly what GameSystem will be used to run the game
// This is great if the framework separates each GameSystem into a separate module, and could add more later on
let gameSystem = GameSystem(game: game)

// In theory, this would print "WiiGameSystem"
print(gameSystem.dynamicType)