repeat while LoopUse the repeat-while loop to continue iterating until a condition is reached. Specify the break keyword.
This page was last reviewed on Aug 21, 2023.
Repeat. Some things in Swift have no known endpoint—we stop them (break the loop) on demand. For a simple loop, we can invoke the "repeat" keyword.
The repeat loop requires a "repeat" and a "while" keyword. To have an infinitely repeating loop, we can use a "while true" part at the end.
First example. Here we have a repeat-while loop. We have a local variable named "i" and we increment this in the body of the repeat-while loop.
Note The loop ends when our variable reaches the value 6. We print the statement "I have N cats" on each iteration.
var i = 0 // Use repeat loop. // ... No initial condition is checked. repeat { print("I have \(i) cats.") i += 1 } while i < 5
I have 0 cats. I have 1 cats. I have 2 cats. I have 3 cats. I have 4 cats.
Repeat, random numbers. Here is a simple program that repeats a function call. It terminates the repeat-while loop only when the function call returns a specific number.
Note Arc4random returns a random number. In the following if-statement, we break if the number is even (not odd).
Tip Consider using a "while-true" loop when an infinite (or indeterminate) loop is needed. A break can stop the loop.
import Foundation // Initialize a seed number. sranddev() // Get random number in repeat loop. // ... Print number. // If number is even then break the loop. repeat { let number = arc4random() print(number) // Check for even number. if number % 2 == 0 { print("Even number, stopping loop.") break } } while true
546090829 4220801392 Even number, stopping loop.
Repeat, example 3. The repeat-while loop does not check its condition before the loop body is entered. So a variable (like "x" in this program) can have any value.
var x = 999 repeat { // This block is entered on any value of x. // ... The value is not checked before the block is executed. print(x) } while x < 10
A summary. The repeat-while loop is the same as a "do-while" loop in C-like languages. The word "repeat" may be easier to read for programmers. Its while part is required.
Dot Net Perls is a collection of tested code examples. Pages are continually updated to stay current, with code correctness a top priority.
Sam Allen is passionate about computer languages. In the past, his work has been recommended by Apple and Microsoft and he has studied computers at a selective university in the United States.
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