break and continue

Two keywords change how a loop runs:

• break stops the loop completely.
• continue skips the rest of the current pass and moves on to the next one.

Example

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

Expected output

1
3
5
7

Even numbers are skipped by continue. When n reaches 9, break ends the loop.

Finding the first match

break is common when searching:

let temperatures = [18, 21, 26, 30, 24]
var firstHotDay: Int?

for (day, temp) in temperatures.enumerated() where temp > 25 {
    firstHotDay = day + 1
    break
}

if let firstHotDay {
    print("First hot day: day \(firstHotDay)")
}

First hot day: day 3

A where clause on a for-in loop filters which items the body runs for. (The Collections lessons show an even shorter way: firstIndex(where:).)

Practice

Print the numbers from 1 to 20, skipping multiples of 3, and stop completely at 16.

for n in 1...20 {
    if n == 16 { break }
    if n % 3 == 0 { continue }
    print(n)
}