Swift - How to know when a loop has ended?

Here is the loop you tried to implement:

func loop() {
  for var i=0; i<5; i++ {
    println(i)
    println("loop has finished")
  }
}

The reason why "loop has finished" gets printed 5 times is because it is within the for-loop.

Anything in between your brackets will be run when the loop repeats (where I entered "enter code here)

for var i=0; i<5; i++ {
   enter code here
 }

The way that loops work is, it will repeat until the condition is completed: i.e. i<5. Your i variable starts at 0 as you stated in var i=0, and every time the loop repeats, this number increases by 1, as stated in i++

Once i is not less than 5 (i is equal to 5 or greater than 5), then the code following your for-loop will be run.

So if you put your println("loop has finished") right after the forloop, you know it will run when the loop is completed, like this:

func loop() {
  for var i=0; i<5; i++ {
    println(i)
  }
  println("loop has finished")
}

The reason why your code doesn't work is because you have the println() statement inside the loop, like this:

func loop() {
  for var i=0; i<5; i++ {
  println(i)
  println("loop has finished")
  }
}

So it prints out "Finished" every time the loop loops.

To fix this, all you need to do is put the println() statement after the loop, like so:

func loop() {
  for var i=0; i<5; i++ {
    println(i)
  }
  println("loop has finished")
}

And voilà. Your app will now function properly!

func loop() {
  for var i=0; i<5; i++ {
    println(i)
  }
  println("loop has finished")
}

To produce the same result as what others have posted but with basic closure syntax:

func printFunction() {
    println("loop has finished")
}

func loopWithCompletion(closure: () -> ()) {
    for var i=0; i<5; i++ {
        println(i)
    }
    closure()
}

This is how you call it:

 loopWithCompletion(printFunction)

Swift 3 Update:

func printFunction() {
    print("loop has finished")
}

// New for loop syntax and naming convention
func loop(withCompletion completion: () -> Void ) {
    for i in 0 ..< 5 {
        print(i)
    }
    completion()
}

Then call it like this:

loop(withCompletion: printFunction)

Or

loop {
    print("this does the same thing")
}