How can I make a function execute every second in swift?

Question

I want to add a score to the top of my scene in the game I am working on. The score is going to based on how long you last, and will increase every second. Thanks for the help in advance!

import SpriteKit  class easyScene: SKScene {     let scrollBarEasyBottom = SKSpriteNode(imageNamed: "scrollBarEasyBottom")     let scrollBarEasyTop = SKSpriteNode(imageNamed: "scrollBarEasyTop")     let ball = SKSpriteNode(imageNamed: "ball")     var origSBEBpositionX = CGFloat(0)     var origSBETpositionX = CGFloat(0)     var maxSBEBX = CGFloat(0)     var SBEBSpeed = 5     var maxSBETX = CGFloat(0)     var SBETSpeed = 5     var score = 0     var timer: NSTimer?          var scoreText = SKLabelNode(fontNamed: "Kailasa")          override func didMoveToView(view: SKView) {         println("Easy Scene is the location")         self.backgroundColor = UIColor.blackColor()         self.scrollBarEasyBottom.position = CGPoint(x:0, y:270)         self.addChild(self.scrollBarEasyBottom)         self.scrollBarEasyBottom.yScale = 0.2         self.origSBEBpositionX = self.scrollBarEasyBottom.position.x         // end scrollBarEasyBottom         self.scrollBarEasyTop.position = CGPoint(x:20, y:400)         self.addChild(self.scrollBarEasyTop)         self.scrollBarEasyTop.yScale = 0.2         self.origSBETpositionX = self.scrollBarEasyTop.position.x         // end scrollBarEasyTop         self.ball.position = CGPoint(x:40, y:293)         self.addChild(self.ball)         self.ball.yScale = 0.17         self.ball.xScale = 0.17         // end ball         self.maxSBEBX = self.scrollBarEasyBottom.size.width - self.frame.size.width         self.maxSBEBX *= -1         self.maxSBETX = self.scrollBarEasyTop.size.width - self.frame.size.width         self.maxSBETX *= -1         //         self.scoreText.text = "0"         self.scoreText.fontSize = 60         self.scoreText.position = CGPoint(x: CGRectGetMidX(self.frame), y: 500)         self.scoreText.text = String(self.score)         self.addChild(self.scoreText)         timer = NSTimer.scheduledTimerWithTimeInterval(1, target: self, selector: Selector("scoreIncrease") , userInfo: nil, repeats: true)         func scoreIncrease (){             score++             println(score)         }     }      override func update(currentTime: NSTimeInterval) {         if self.scrollBarEasyBottom.position.x <= maxSBEBX + 1200 {             self.scrollBarEasyBottom.position.x = self.origSBEBpositionX         }         if self.scrollBarEasyTop.position.x <= maxSBETX + 1200 {             self.scrollBarEasyTop.position.x = self.origSBETpositionX         }                  scrollBarEasyBottom.position.x -= CGFloat(self.SBEBSpeed)         scrollBarEasyTop.position.x -= CGFloat(self.SBETSpeed)         // moving bars         var degreeRotation = CDouble(self.SBEBSpeed) * M_PI / 180         self.ball.zRotation -= CGFloat(degreeRotation)         //rotate ball     }         } 

After running this code, I always get an

unrecognized selector sent to instance error

Answer 1

You can use one like this:

var timer = NSTimer()  override func viewDidLoad() {     scheduledTimerWithTimeInterval() }  func scheduledTimerWithTimeInterval(){     // Scheduling timer to Call the function "updateCounting" with the interval of 1 seconds     timer = NSTimer.scheduledTimerWithTimeInterval(1, target: self, selector: Selector("updateCounting"), userInfo: nil, repeats: true) }        func updateCounting(){     NSLog("counting..") } 

---

Swift 3:

var timer = Timer()  override func viewDidLoad() {               // Use for the app's interface     scheduledTimerWithTimeInterval() }  override func didMove(to view: SKView) {    // As part of a game     scheduledTimerWithTimeInterval() }  func scheduledTimerWithTimeInterval(){     // Scheduling timer to Call the function "updateCounting" with the interval of 1 seconds     timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(self.updateCounting), userInfo: nil, repeats: true) }  @objc func updateCounting(){     NSLog("counting..") } 

---

Swift 5:

Note: this solution is compatible with iOS 10.0+.

// If needing to check for iOS compatibility use // if #available(iOS 10.0, *) {code}  var timer = Timer()  override func viewDidLoad() {     self.timer = Timer.scheduledTimer(withTimeInterval: 1, repeats: true, block: { _ in         updateCounting()     }) }  func updateCounting(){     print("counting...") } 

You can then invalidate (stop) the timer using:

timer.invalidate() 

Answer 2

There is something called NSTimer in swift which could solve your problem. I have given an example like how you can use it. Just customise it for your purpose.

var timer = NSTimer.scheduledTimerWithTimeInterval(1.0,                                                     target: self,                                                     selector: Selector("yourMethodToCall"),                                                     userInfo: nil,                                                     repeats: true) 

Add this line to the place where you need to call your function repeatedly.

1. The 1.0 refers to 1 second.
2. Change the selector to call yourMethodName
3. repeats is set to true to call that function every second.

Try this out and let me know if your are stuck somewhere. Thanks.