How to access for loop externally and make it stop in swift - ios

Question

I'm using this function to make the text write letter by letter:
extension SKLabelNode {
func setTextWithTypeAnimation(typedText: String, characterInterval: NSTimeInterval = 0.05) {
text = ""
self.fontName = "PressStart2P"
dispatch_async(dispatch_get_global_queue(QOS_CLASS_USER_INTERACTIVE, 0)) {
for character in typedText.characters {
dispatch_async(dispatch_get_main_queue()) {
self.text = self.text! + String(character)
}
NSThread.sleepForTimeInterval(characterInterval)
}
}
}
And, if the user clicks the screen, I want to make the for loop stop and show the complete text instantly.

Answer 1

I would do something like this:
var ignoreSleeper = false
#IBAction func pressButton(sender: UIButton) {
ignoreSleeper = true
}
extension SKLabelNode {
func setTextWithTypeAnimation(typedText: String, characterInterval: NSTimeInterval = 0.05) {
text = ""
self.fontName = "PressStart2P"
dispatch_async(dispatch_get_global_queue(QOS_CLASS_USER_INTERACTIVE, 0)) {
for character in typedText.characters {
dispatch_async(dispatch_get_main_queue()) {
self.text = self.text! + String(character)
}
if(!ignoreSleeper){
NSThread.sleepForTimeInterval(characterInterval)
}
}
}
}
Edit: like #Breek already mentioned

Answer 2

I'd suggest to implement a tiny NSTimer with a counter for the number of chars to display. Start the Timer with a repeat count of typedText.characters.count and the desired delay and you're good to go (with one thread). Increment the number of chars counter on each timer loop. You can stop this timer at any time with a button press by calling invalidate on the timer.
Example
var timer: NSTimer?
var numberOfCharsToPrint = 1
let text = "Hello, this is a test."
func updateLabel() {
if numberOfCharsToPrint == text.characters.count {
welcomeLabel.text = text
timer?.invalidate()
}
let index = text.startIndex.advancedBy(numberOfCharsToPrint)
welcomeLabel.text = text.substringToIndex(index)
numberOfCharsToPrint++;
}
Then initialize your timer whenever you want the animation to start.
timer = NSTimer.scheduledTimerWithTimeInterval(0.25, target: self, selector: "updateLabel", userInfo: nil, repeats: true)
You can invalidate/stop the timer at any given time with timer?.invalidate().