Delay loop calling animation process - swift

Question

Here is a section of my code where I am trying to delay a function called dropText that drops a name from the top of the screen. I tried using a delay function but it delays then drops them all at once. What am I missing, or is this method just plain wrong? Thanks in advance:
func delay(_ delay:Double, closure:#escaping ()->()) {
DispatchQueue.main.asyncAfter(
deadline: DispatchTime.now() + Double(Int64(delay * Double(NSEC_PER_SEC))) / Double(NSEC_PER_SEC), execute: closure)
}
//New group choose method
func groupChoose()
{
//loop through the players
for x in 0...players - 1{
//drop the name in from the top of the screen
delay(2.0) {
self.dropText(playing[x])
}
}

Answer 1

This issue is because you are delaying all of them at once! You should try to assign different delay time to each one:
for x in 1...players {
//drop the name in from the top of the screen
delay(2.0 * x) {
self.dropText(playing[x-1])
}
Refactored
Try to not call array elements by index:
for playing in playing.enumerated() {
// drop the name in from the top of the screen
let player = playing.offset + 1
delay(2.0 * player) {
self.dropText(playing.element)
}

Answer 2

Look at the loop. You are calling asyncAfter almost immediately one after another. So the text is dropped after the delay almost immediately one after another, too.
I recommend to use a Timer
func delay(_ delay: Double, numberOfIterations: Int, closure:#escaping (Int) -> Void) {
var counter = 0
Timer.scheduledTimer(withTimeInterval: delay, repeats: true) { timer in
DispatchQueue.main.async { closure(counter-1) }
counter += 1
if counter == numberOfIterations { timer.invalidate() }
}
}
and
func groupChoose()
{
delay(2.0, numberOfIterations: players) { counter in
self.dropText(playing[counter])
}
}