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.

Answer 3

Swift 3

find this solution it worked for me

weak var timer: Timer?
var timerDispatchSourceTimer : DispatchSourceTimer?

func startTimer() {
    if #available(iOS 10.0, *) {
        timer = Timer.scheduledTimer(withTimeInterval: 3, repeats: true) { [weak self] _ in
            // do something here

        }

    } else {
        // Fallback on earlier versions
        timerDispatchSourceTimer = DispatchSource.makeTimerSource(flags: [], queue: DispatchQueue.main)
        timerDispatchSourceTimer?.scheduleRepeating(deadline: .now(), interval: .seconds(60))
        timerDispatchSourceTimer?.setEventHandler{
                // do something here

        }
        timerDispatchSourceTimer?.resume()
    }
}

func stopTimer() {
    timer?.invalidate()
    //timerDispatchSourceTimer?.suspend() // if you want to suspend timer 
    timerDispatchSourceTimer?.cancel()
}

// if appropriate, make sure to stop your timer in `deinit`
deinit {
    stopTimer()
}

Answer 4

I prefer

var timer: Timer?

override func viewDidLoad() {
    super.viewDidLoad()          

    timer =  Timer.scheduledTimer(withTimeInterval: 1.0, repeats: true) { (timer) in                
        // Do what you need to do repeatedly         
    }
}

To stop it:

override func viewWillDisappear(_ animated: Bool) {
    super.viewWillDisappear(animated)

    if timer != nil {
        timer?.invalidate()
        timer = nil
    }
}

Answer 5

Xcode 10.2 Swift 5:

override func viewDidLoad() {
    super.viewDidLoad()
    // ...
    Timer.scheduledTimer(timeInterval: 8.0, target: self, selector: Selector(("your @obcj func name")), userInfo: nil, repeats: true)
}

//Anywhere in the same view controller to stop the loop:
Timer.cancelPreviousPerformRequests(withTarget: your @obcj func name())

Answer 6

I don't think you need NSTimer for this.

Since you are using SpriteKit, I am going to suggest simplest solution in my opinion:

Declare a variable var prevScoreCalcTime:TimeInterval = 0

Inside of update func in your GameScene set it up like below:

override func update(_ currentTime: TimeInterval) {
    if currentTime - prevScoreCalcTime > 1 {
        prevScoreCalcTime = currentTime
        // Any function you put here will execute every second
    }
}

Good luck!

Answer 7

// For running a piece of code every second

///Runs every second, to cancel use: timer.invalidate()
@discardableResult public static func runThisEvery(
    seconds: TimeInterval,
    startAfterSeconds: TimeInterval,
    handler: @escaping (CFRunLoopTimer?) -> Void) -> Timer {
    let fireDate = startAfterSeconds + CFAbsoluteTimeGetCurrent()
    let timer = CFRunLoopTimerCreateWithHandler(kCFAllocatorDefault, fireDate, seconds, 0, 0, handler)
    CFRunLoopAddTimer(CFRunLoopGetCurrent(), timer, CFRunLoopMode.commonModes)
    return timer!
}