引用类名作为变量

Question

我想知道是否有更好的方法来编写这段代码。这是非常多余的，在我这样做之前，我认为应该有一种方法可以使用变量作为类名，但遇到了很多问题并最终以这种方式结束。现在每次看都觉得很烦。我对这个主题进行了相当多的研究，但没有提出任何建议。可能是因为我不确定这样做会被称为什么。

为了论证，假设下面的代码在一个函数中，当一个 SKSpriteNode 被点击时被调用。每个“按钮”都以其将要转换到的场景命名。实际上还有 12 个这样的 case 语句。

let name = sender.name
switch(name){
    case "newGame":
        defaults.set(true,forKey: "isFirstRun")
        defaults.set(true,forKey: "isNewGame")
        let transition = SKTransition.crossFade(withDuration: 1.0)
        let nextScene = Setup(fileNamed:"Setup")
        nextScene?.scaleMode = .aspectFill
        scene?.view?.presentScene(nextScene!, transition: transition)
        break
    case "IceFishing":
        defaults.set(2, forKey: "currentLocation")
        let transition = SKTransition.crossFade(withDuration: 1.0)
        let nextScene = IceFishing(fileNamed:"IceFishing")
        nextScene?.scaleMode = .aspectFill
        scene?.view?.presentScene(nextScene!, transition: transition)
        break
    case "OpeningScene":
        let transition = SKTransition.crossFade(withDuration: 1.0)
        let nextScene = OpeningScene(fileNamed:"OpeningScene")
        nextScene?.scaleMode = .aspectFill
        scene?.view?.presentScene(nextScene!, transition: transition)
        break
    case "House":
        let transition = SKTransition.crossFade(withDuration: 1.0)
        let nextScene = SodHouse(fileNamed:"House")
        nextScene?.scaleMode = .aspectFill
        scene?.view?.presentScene(nextScene!, transition: transition)
        break
    default:
        break
}

我认为（或希望）有一种方法可以做类似...

let name = sender.name
let _Class = name as! SKScene //Not right, but i was guessing

let transition = SKTransition.crossFade(withDuration: 1.0)
let nextScene = _Class(fileNamed:name)
nextScene?.scaleMode = .aspectFill
scene?.view?.presentScene(nextScene!, transition: transition)

所有 sks 文件和 Swift 类的名称都相同。

Answer 1

您基本上希望代码看起来像这样（我为您添加了一些守卫）：

let name = sender.name
let transition = SKTransition.crossFade(withDuration: 1.0)
guard let nextScene = SKScene(fileNamed:sender.name) else {fatalError("unable to find next scene")}
guard let scene = scene else {fatalError("unable to find scene")}
guard let view = scene.view else {fatalError("unable to find view")}

nextScene.scaleMode = .aspectFill

case "newGame":
    //I would avoid using defaults unless you plan on saving when the app exits
    defaults.set(true,forKey: "isFirstRun")
    defaults.set(true,forKey: "isNewGame")

case "IceFishing":
    defaults.set(2, forKey: "currentLocation")

default: break
}

view.presentScene(nextScene!, transition: transition)

我们所做的基本上是依靠 sks 文件中的自定义类字段来为我们加载自定义类。

编辑：现在为了进一步清理代码，我会放弃使用默认值。只有当您想跨游戏会话而不是跨游戏保存数据时，您才应该使用它。

let name = sender.name
let transition = SKTransition.crossFade(withDuration: 1.0)
guard let nextScene = SKScene(fileNamed:sender.name) else {fatalError("unable to find next scene")}
guard let scene = scene else {fatalError("unable to find scene")}
guard let view = scene.view else {fatalError("unable to find view")}

nextScene.scaleMode = .aspectFill

nextScene.userData += scene.userData
//Move these to the SKS file under UserData section, then you can pull it using scene.userData?
//    defaults.set(2, forKey: "currentLocation")    
//    defaults.set(true,forKey: "isFirstRun") 
//    defaults.set(true,forKey: "isNewGame")

view.presentScene(nextScene!, transition: transition)