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

All these answers are not that helpful actually. In SpriteKit you should consider using SKactions for time related stuff. Search about this on SO. In general, a Timer (NSTimer) doesn't respect node's, scene's, or view's paused state, so it can lead into certain issues. On the other side, SKActions are paused automatically if node, scene or a view is paused during a game or at certain interruptions like a phone call etc. — Whirlwind

Mohammad Nurdin Mohammad Nurdin · Accepted Answer · 2015-05-07T08:05:06

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 the timer using:

timer.invalidate()

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

7 Answers