Swift: How to stop timers started from a loop? - ios

Question

I got some Swift code to print every character of a specific word ("stackoverflow") and also with a specific delay (1.0s).
To understand my thoughts look at the pseudo code:
print("s")
wait(1s)
print("t")
wait(1s)
print("a")
wait(1s)
print("c")
wait(1s)
print("k")
wait(1s)
...
Ok - below you can find my code written in Swift:
var mystring="stackoverflow"
var counter=0.0
for i in mystring {
Timer.scheduledTimer(
timeInterval: Double(counter),
target: self,
selector: #selector(self.myfunc(_:)),
userInfo: String(i),
repeats: false)
counter=counter+1.0
})
}
func myfunc(_ timer: Timer) {
let value: String? = timer.userInfo! as? String
print ("Value: \(value as String?)")
}
But how is it possible to kill all myfunc-calls after the for loop has finished? How to kill the different Timers that I didn't declared with a variable to avoid the override of the last Timer??

Answer 1

Why not one timer and a few lines additional logic. The code prints the first character of the string when the timer fires and then drops the first character until the string is empty. At the end the timer gets invalidated.
let string = "stackoverflow"
var temp = Substring(string)
Timer.scheduledTimer(withTimeInterval: 1.0, repeats: true) { timer in
print(temp.prefix(1))
temp = temp.dropFirst()
if temp.isEmpty { timer.invalidate() }
}
or as ticker
let string = "stackoverflow"
var counter = 1
Timer.scheduledTimer(withTimeInterval: 1.0, repeats: true) { timer in
print(string.prefix(counter))
if counter == string.count { timer.invalidate() }
counter += 1
}

Answer 2

Edit : For those who argue that this is not the best answer it's the best for his current programming technique and to suggest a good one here is a solution in edit part for his main issue with no timers at all
Edit://////
var counter = 0.0
for i in mystring {
DispatchQueue.main.asyncAfter(deadline: .now() + counter) {
print("\(String(i))")
}
counter = counter + 1
}
/////////
declare var
var timerarr = [Timer] = []
then add every created timer to the array
for i in mystring {
let t = Timer.scheduledTimer(
timeInterval: Double(counter),
target: self,
selector: #selector(self.myfunc(_:)),
userInfo: String(i),
repeats: false)
counter=counter+1.0
})
timerarr.append(t)
}
and loop to stop
for i in 0..<timerarr.count {
let tim = timerarr[i]
tim.invalidate()
}
timearr = []