class ContentsViewController: UIViewController {
    var text: String?

    @IBOutlet weak var skView: SKView!

    override func viewDidLoad() {
        super.viewDidLoad()
        self.view.backgroundColor = UIColor.grayColor()
        self.setupParticle()
    }

    func setupParticle() {
        //skView.allowsTransparency = true // 今回は不要。普通はtrueにする。
        //skView.userInteractionEnabled = false // 今回は不要。必要であればfalseにする。
        let scene = ParticleScene.unarchiveFromFile("ParticleScene") as! ParticleScene
        skView.presentScene(scene)
    }

    override func viewDidAppear(animated: Bool) {
        super.viewDidAppear(animated)
        let scene = self.skView.scene as! ParticleScene
        if let t = text {
            scene.show(t)
        }
    }
}

extension SKNode {
    class func unarchiveFromFile(file : NSString) -> SKNode? {
        if let path = NSBundle.mainBundle().pathForResource(file as String, ofType: "sks") {
            let sceneData = try! NSData(contentsOfFile: path, options: .DataReadingMappedIfSafe)
            let archiver = NSKeyedUnarchiver(forReadingWithData: sceneData)
            archiver.setClass(self.classForKeyedUnarchiver(), forClassName: "SKScene")
            let myScene = archiver.decodeObjectForKey(NSKeyedArchiveRootObjectKey) as! ParticleScene
            archiver.finishDecoding()
            return myScene
        } else {
            return nil
        }
    }
}

class ParticleScene: SKScene {
    func show(type: String) {
        if (self.children.count == 0) {
            guard let path = NSBundle.mainBundle().pathForResource("\(type)Particle", ofType: "sks") else {
                return
            }
            let particle = NSKeyedUnarchiver.unarchiveObjectWithFile(path) as! SKEmitterNode
            particle.position = CGPointMake(CGRectGetMidX(self.frame), CGRectGetMidY(self.frame))
            self.addChild(particle)
        }
    }
}