Swift: Simplify menu button logic

问题

I have a game in Swift where each of my levels is a separate class inherited from the base GameScene class (it's a lot easier this way for what I'm doing, don't judge me). I also have a menu which has a button for each level. This is how the buttons loads the level:

override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
  if let t = touches.first {
    let node = atPoint(t.location(in: self))
    if let name = node.name {
      let newScene: GameScene!
      switch Int(name)! {
      case 1:
        newScene = Level1(size: frame.size)
      case 2:
        newScene = Level2(size: frame.size)
      case 3:
        newScene = Level3(size: frame.size)
      case 4:
        newScene = Level4(size: frame.size)
      case 5:
        newScene = Level5(size: frame.size)
      case 6:
        newScene = Level6(size: frame.size)
      case 7:
        newScene = Level7(size: frame.size)
      default:
        newScene = Level1(size: frame.size)
      }
      view?.presentScene(newScene, transition: .crossFade(withDuration: 0.5))
    }
  }
}

To me, this switch looks incredibly ugly and pointless, but I can't think of a way to avoid it. I was hoping someone here could help me out with this, I just can't think of a better alternative.

回答1:

You could construct your Level's class name as a string "Level\(name)" first and then get the actual class you need by passing it's name to the function:

func classFromString(_ className: String) -> AnyClass! {
    let namespace = Bundle.main.infoDictionary!["CFBundleExecutable"] as! String
    let cls: AnyClass = NSClassFromString("\(namespace).\(className)")!
    return cls
}

Usage example:

let className = "Level1"
let levelInstance = (classFromString(className) as! GameScene).init(size: frame.size)

... but of course the best advice would be to avoid such kind of architecture

回答2:

You can do this instead:

    var newScene: GameScene!

    //Level1 is repeating on 0 and 1'st index

    let arrScene : [GameScene] = [Level1(size: frame.size),Level1(size: frame.size),Level2(size: frame.size),Level3(size: frame.size),Level4(size: frame.size),Level5(size: frame.size),Level6(size: frame.size),Level7(size: frame.size)]

    if Int(name)! <=7 && Int(name)! > 0{

    newScene  = arrScene[Int(name)!]

    }else{

    //Default level1 
    newScene  = arrScene[0]

    }

来源：https://stackoverflow.com/questions/44426024/swift-simplify-menu-button-logic