This tutorial belongs to the Swift series

for-in loops can be used to iterate a specific amount of times, using a range operator:

for index in 0...3 {
  //iterate 4 times, `index` is: 0, 1, 2, 3
}

You can iterate over the elements of an array or set:

let list = ["a", "b", "c"]
for item in list {
  // `item` contains the element value
}

And on the elements of a dictionary:

let list = ["a": 1, "b": 2, "c": 2]
for (key, value) in list {
  // `key` contains the item key
  // `value` contains the item value
}