Swift Tutorial - Tutorialspoint

The key point of a while loop is that the loop might not ever run. When the condition is
tested and the result is false, the loop body will be skipped and the first statement after
the while loop will be executed.

Example

import Cocoa

var index = 10

while index < 20

{

println( "Value of index is \(index)")

index = index + 1

}

Here we are using comparison operator < to compare the value of the variable index
against 20. While the value of index is less than 20, the while loop continues executing a
block of code next to it and as soon as the value of index becomes equal to 20, it comes
out. When executed, the above code produces the following result:

Value of index is 10

Value of index is 11

Value of index is 12

Value of index is 13

Value of index is 14

Value of index is 15

Value of index is 16

Value of index is 17

Value of index is 18

Value of index is 19

Swift – do-while Loop

Unlike for and while loops, which test the loop condition at the top of the loop,
the do...while loop checks its condition at the bottom of the loop.

A do...while loop is similar to a while loop, except that a do...while loop is guaranteed
to execute at least once.