Using dispatchQueue in loops - swift

Question

I am attempting to loop something with a delay (just as a proof of concept) this is for something else. But to simplify it, here is an example.
so in this example, I have a string with "text" and I want to loop the addition of another string lets say 10 times. The only thing is that I want there to be a delay in each iteration. here is my code thus far.
// global variable
var myString = "text"
// an action inside a button
let delayInSeconds = 1.0
DispatchQueue.main.asyncAfter(deadline: DispatchTime.now() + delayInSeconds) {
for _ in 1...10 {
self.myString += "another text"
}
}
labelOne.text = myString
}
I should add that the result is that all 10 "another text" are added immediately without any delay.
thank you

Answer 1

In your example, you append your string ten times in the same work unit. Try dispatching work once per loop:
for delay in 1...10 {
let delayInSeconds = Double(delay)
DispatchQueue.main.asyncAfter(deadline: DispatchTime.now() + delayInSeconds) {
self.myString += "another text"
labelOne.text = myString
}
}
This loop won't work well for arbitrarily large values, though. It also doesn't provide the kind of precise timing we might want for user interface changes. For that, we can use Timer. Here’s the same problem reworked with Timer:
// Add to the class body…
var i = 1
// Lazy initialization so the timer isn’t initialized until we call it
lazy var timer = Timer.scheduledTimer(withTimeInterval: 1.0, repeats: true) {timer in
guard self.i <= 20 else {
timer.invalidate()
return
}
self.label.text?.append(" another text")
self.i += 1
}
// Add to the button action…
timer.fire()

Answer 2

If I understand correctly, you want to show the text one by one with delay for each “text”.
You can use recursion here.
1.Move the dispatch code into a method.
2. Remove for loop.
3. Do your necessary actions inside dispatch it.
4.call that same method again inside dispatch.
Do remember to use a counter variable that increments each time method is called. Use it to break the recursion.