Welcome to the Treehouse Community

The Treehouse Community is a meeting place for developers, designers, and programmers of all backgrounds and skill levels to get support. Collaborate here on code errors or bugs that you need feedback on, or asking for an extra set of eyes on your latest project. Join thousands of Treehouse students and alumni in the community today. (Note: Only Treehouse students can comment or ask questions, but non-students are welcome to browse our conversations.)

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and a supportive community. Start your free trial today.

iOS Swift Collections and Control Flow Control Flow With Loops While and Repeat While

I was just wondering if anyone could break this down and explain to me how this works...?

let numbers = [2,8,1,16,4,3,9] var sum = 0 var counter = 0

while counter < numbers.count { sum += numbers[counter] counter += 1}


Thank You! That makes so much sense now.

1 Answer

Hey Michael, I've posted your code with my comments below. Hope this helps.

//declares an array of Int's named numbers
let numbers = [2,8,1,16,4,3,9]
//declares an Int variable named sum, initialised with a zero value
//used to keep track of the sum total
var sum = 0
//declares an Int variable named counter, initialised with a zero value
//this is used as an index value, as well as an indicative value
//to compare to the number of items in the numbers array
var counter = 0

//While Loop
//This should read as "While the counter is less than the amount of items in the numbers array, execute the below."
//While this conditional is true, the body of the loop will execute.
while counter < numbers.count {
    //The += operator takes the current value of sum, and adds
    //the number at the index specified by the counter property.
    //can also be written as sum = sum + numbers[counter]
    sum += numbers[counter]
    //We then add 1 onto the current counter property so that
    //the index next time will be one more than this execution.
    //If this was the last index in the array, the boolean
    //of the while loop condition will become false and stop executing
    //because the counter is now higher than the amount of items in the numbers array.
    counter += 1