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iOS Swift Basics (retired) Control Flow Exercise: FizzBuzz Generator

Posted by val
val
585 Points

Why do we have to use " for kid in kids " and why cant we just write " let kids = 1...10 if kid % 3 == 0

My code: let kids = 1...10

for kid in kids { if kid % 3 == 0 && kid % 5 == 0 {println("FizzBuzz")} else if kid % 3 == 0 {println("Fizz")} else if kid % 5 == 0 {println("Buzz")} else {println(kid)} }

This is correct, but hy can't I leave out the "for kid in kids" part? like this:

let kids = 1...10

if kid % 3 == 0 && kid % 5 == 0 {println("FizzBuzz")}
else if kid % 3 == 0 {println("Fizz")}
else if kid % 5 == 0 {println("Buzz")}
else {println(kid)}

I know it's not correct but I can't explain why, please help.

Luke Evans
Luke Evans
Courses Plus Student 526 Points

I think it's because you haven't defined "kid" anywhere, so the computer has no idea what "kid" actually is. If you changed the constant at the top to "let kid = 1...10" (rather than "let kids= 1...10"), it still wouldn't work: you have defined it as a range of numbers, not an individual number that could be divided by 3 or 5.

The for-in loop defines this "kid" value for you. It takes the individual numbers in the "kids" range of numbers and then, in the { }, it does all the things you've asked it to do (i.e. check the remainders of these individual numbers when divided by 3, etc.)

Hope this helps!

2 Answers

Dan Chambers
Dan Chambers
6,057 Points
Dan Chambers
Dan Chambers
6,057 Points

If I understand correctly, the whole point of the 'for-in' loop over the regular 'for' loop is to save on code when you need to iterate through a range or array, because this is such a common task. I think there's a lot happening under the hood that makes it difficult to grasp. I think the example confuses things by using the word 'kid'. I prefer to use 'i' to represent the index like this:

let kids = 1...10
for i in kids { //rest of solution }

The reason the above works is because the declaration, condition, and increment are all implied when you use the 'For-In' loop. I understand it to essentially be shorthand for the below:

let kids = 1...10
for var i = 1; i < kids.count; ++i { //rest of solution }

Hope that explains whats actually happening. I find looking to the Apple documentation straight after a video very useful to iron these things out.

Sameer Vohra
Sameer Vohra
754 Points
Sameer Vohra
Sameer Vohra
754 Points

Took me a bit of thinking to make the same change Dan suggested, but it is a massive improvement, especially for new programmers. Was going to email Treehouse, but figured they won't re make the video and I saw Dan's post here. Hopefully more people see this if they get stuck on the logic.