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Loops

Ranges

Ranges created by the ... operator will include the numbers from the lower bound to (and includes) the upper bound.

let zeroToThree = 0...3


// zeroToThree: 0, 1, 2, 3

stride() Function

Calling stride() with the 3 necessary arguments creates a collection of numbers; the arguments decide the starting number to, the (excluded) ending number, and how to increment/decrement from the start to the end. 

for oddNum in stride(from: 1, to: 5, by: 2) {
  print(oddNum)
}


// Prints: 1
// Prints: 3

for-in Loop

The for-in loop is used to iterate over collections, including strings and ranges. 

for char in "hehe" {
  print(char)
}


// Prints: h
// Prints: e
// Prints: h
// Prints: e

continue Keyword

The continue keyword will force the loop to move on to the next iteration. 

for num in 0...5 {
  if num % 2 == 0 {
    continue
  }
  print(num)
}


// Prints: 1
// Prints: 3
// Prints: 5

break Keyword

To terminate a loop before its completion, use the break keyword. 

for char in "supercalifragilisticexpialidocious" {
  if char == "c" {
    break
  }
  print(char)
}


// Prints: s
// Prints: u
// Prints: p
// Prints: e
// Prints: r

Using Underscore

Use _ instead of a placeholder variable if the variable is not referenced in the for-in loop body.

for _ in 1...3 {
  print("Olé")
}


// Prints: Olé
// Prints: Olé
// Prints: Olé

while Loop

A while loop accepts a condition and continually executes its body’s code for as long as the provided condition is true.

If the condition is never false then the loop continues to run and the program is stuck in an infinite loop.

var counter = 1
var stopNum = Int.random(in: 1...10)


while counter < stopNum {
  print(counter)
  counter += 1
}


// The loop prints until the stop condition is met
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