How do I iterate a loop with time delays in Swift - ios

Question

So basically I'm trying to print the word "yo" 20 times with a 2 second time delay between each iteration. This is what I came up with which doesn't work
var j = 0
while(j < 20){
print("yo")
let seconds = 2.0
let delay = seconds * Double(NSEC_PER_SEC)//nanoseconds per seconds
let time = dispatch_time(DISPATCH_TIME_NOW, Int64(delay))
dispatch_after(time, dispatch_get_main_queue()) {
j+=1
}
}
Who knows the right way to go about this? Thanks in advance.

Answer 1

Try this. It creates 20 print yo closures at one time instead of serially delaying between each one.
let delay = 2.0 * Double(NSEC_PER_SEC)
(1...20).map {
iteration in
let time = dispatch_time(DISPATCH_TIME_NOW, Int64(delay * Double(iteration)))
dispatch_after(time, dispatch_get_main_queue()) {
print("yo")
}
}

Answer 2

Your code is close. You need to put the print statement inside the dispatch_after:
var j: UInt64 = 0
let seconds: UInt64 = 1
while(j < 10)
{
let delay = seconds * j * NSEC_PER_SEC //nanoseconds per seconds
let time = dispatch_time(DISPATCH_TIME_NOW, Int64(delay))
dispatch_after(time, dispatch_get_main_queue())
{
print("yo")
}
j += 1
}
print("Should start \"yo'ing\" soon")
Also your math was off. the delay value to dispatch_time is a UInt64, not a double.
Note that the code above probably won't work in a playground, since as soon as the main code path finishes, it terminates.

Answer 3

You may try this function
func repeatedPrint(count: Int, withDelay delay: Double)
{
let time = dispatch_time(DISPATCH_TIME_NOW, Int64(delay * Double(NSEC_PER_SEC)))
dispatch_after(time, dispatch_get_main_queue())
{
if count < 1 {return}
print("yo")
self.repeatedPrint(count - 1, delay: delay)
}
}
repeatedPrint(20, delay: 2)