Swift loop from upper value to lower value

Question

I have a Swift for loop defined like this:

 for i in 20...1 {
    array.append(i)
 }

But I get a crash with message

  Thread 1: Fatal error: Can't form Range with upperBound < lowerBound

What is the fix?

@Carpsen90 You should write this up as an answer because it is the best one in terms of getting what the questioner wants in terms of the array, although it technically doesn't answer the question as posed. — JeremyP, Nov 06 '18 at 12:58
@Carpsen90 Never mind then. Your answer is still the best one for this use-case. — JeremyP, Nov 06 '18 at 13:05

score 11 · Answer 1 · answered Nov 06 '18 at 08:17

11

You need to reverse the range:

for i in (1...20).reversed() {
    array.append(i)
}

answered Nov 06 '18 at 08:17

Gereon

score 3 · Answer 2 · edited Nov 06 '18 at 11:29

3

You cannot loop in reverse order like that, if you want you can try this :

for i in stride(from: 20, through: 1, by: -1) {
    array.append(i)
}

edited Nov 06 '18 at 11:29

JeremyP

answered Nov 06 '18 at 08:18

Tung Vu Duc

2

Why do people upvote without checking?! This doesn't include `1` and doesn't add elements to `array` – ielyamani Nov 06 '18 at 10:28
@Carpsen90 I've fixed it. – JeremyP Nov 06 '18 at 11:29
@Carpsen90 thank you, I just wanna show him how to loop in reverse order – Tung Vu Duc Nov 06 '18 at 12:12

2 Answers2