Falling Snow

SnowScene.swift

//
//  SnowView.swift
//  fallingsnow
//
//  Created by JungMin Ahn on 2015. 11. 19..
//  Copyright © 2015년 SmartStudy. All rights reserved.
//

import UIKit
import SpriteKit

class SnowScene: SKScene {

    private var presentingView: SKView?
    private var emitter: SKEmitterNode?

    override func didMoveToView(view: SKView) {
        super.didMoveToView(view)
        scaleMode = .ResizeFill
        backgroundColor = UIColor.clearColor()
        presentingView = view
    }

    func startEmitter() {
        emitter = SKEmitterNode(fileNamed: "snow.sks")
        guard
            let emitter = emitter,
            let presentingView = presentingView
            else { return }
        
        emitter.particlePositionRange = CGVectorMake(CGRectGetWidth(presentingView.bounds), 0)
        emitter.position = CGPointMake(CGRectGetMidX(presentingView.bounds), CGRectGetHeight(presentingView.bounds))
        emitter.targetNode = self

        addChild(emitter)
    }

    func stopEmitter() {
        guard let emitter = emitter else { return }
        emitter.particleBirthRate = 0.0
        emitter.targetNode = nil
        emitter.removeFromParent()
        self.emitter = nil
    }
}

ViewController.swift

//
//  ViewController.swift
//  fallingsnow
//
//  Created by JungMin Ahn on 2015. 11. 19..
//  Copyright © 2015년 SmartStudy. All rights reserved.
//

import UIKit
import SpriteKit

class ViewController: UIViewController {

    @IBOutlet weak private var snowView: UIView!
    private var sceneView: SKView?
    private var snowScene: SnowScene?

    override func viewDidLoad() {
        super.viewDidLoad()

        sceneView = SKView(frame: self.view.frame)
        snowScene = SnowScene()
        guard
            let sceneView = sceneView,
            let snowScene = snowScene
            else { return }
        sceneView.backgroundColor = UIColor.clearColor()
        sceneView.presentScene(snowScene)
        snowView.addSubview(sceneView)
        
        sceneView.userInteractionEnabled = false
		snowView.userInteractionEnabled = false
    }

    override func viewDidAppear(animated: Bool) {
        super.viewDidAppear(animated)
        guard let snowScene = snowScene else { return }
        snowScene.startEmitter()
    }

    override func viewDidDisappear(animated: Bool) {
        super.viewDidDisappear(animated)
        guard
            let snowScene = snowScene,
            let sceneView = sceneView
            else { return }
        sceneView.presentScene(nil)
        sceneView.removeFromSuperview()
        snowScene.stopEmitter()
    }
}