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iOS Swift Basics (retired) Control Flow Comparison and Logical Operators

Harold Bellemare
Harold Bellemare
1,466 Points
Posted by Harold Bellemare
Harold Bellemare
1,466 Points

If/if else clause order (spoiler)

Hopefully my question will make sense.

At first, I tried to follow Amit's instructions sequentially:

  1. If number is divisible by 3, print Fizz
  2. If number is divisible by 5, print Buzz
  3. If number is divisible by both, print FizzBuzz

However, my code would only run if I followed the order 3-1-2, as someone else did in another thread here. Am I missing something, here? Here is what I mean... this is my working code:

import UIKit

let set = 1...20
let f = "Fizz"
let b = "Buzz"

for number in set {
    if (number % 3 == 0) && (number % 5 == 0) {
        print("\(number)\t\(f)\(b)!")
    } else if (number % 3 == 0) {
        print("\(number)\t\(f)!")
    } else if (number % 5 == 0) {
        print("\(number)\t\(b)!")
    } else {
        print(number);
    }
}

1 Answer

Ryan Lail
Ryan Lail
4,386 Points

Hi Harold,

This is due to the logic of the if statements. If it first takes the number 15 for example and asks if it's divisible by 5, it will say yes and move on to the next number - without asking if it's divisible by 3 or both. That's why you must first ask, 'is number divisible by both 3 and 5'. You can then put the remaining two statements in any order as the number simply can't be divisible by both as if it was, it would have been picked up by your first if statement.

I hope that makes sense - just leave a comment if you need more clarity.

~Ryan.