Loops

Swift has two loop forms: for-in, built around iterating a sequence (a range, an array, anything else that's iterable), and while, for repeating until a condition changes. There's no C-style three-part for loop in Swift at all.

for-in over a range

Swift main.swift

for i in 1...5 {
    print("Count: \(i)")
}

Output

Count: 1
Count: 2
Count: 3
Count: 4
Count: 5

1...5 is a closed range that includes both ends. Swap it for 1..<5 (a half-open range) if you want to stop before 5 instead of at it.

for-in over an array

Swift main.swift

let fruits = ["apple", "banana", "cherry"]

for fruit in fruits {
    print(fruit)
}

Output

apple
banana
cherry

while

Swift main.swift

var stock = 100

while stock > 0 {
    stock -= 30
}

print("Stock ended at \(stock)")

Output

Stock ended at -20

break and continue

Swift main.swift

for n in 1...10 {
    if n % 2 == 0 {
        continue
    }
    if n > 7 {
        break
    }
    print(n)
}

Output

Note: \(i) inside a string literal is string interpolation — it evaluates i and splices its text representation directly in, the same job template literals do in JavaScript with ${}. You'll see it constantly in idiomatic Swift instead of concatenating strings with +.

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