Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

iOS Closures in Swift 2 First Class Functions Higher Order Functions

16,353 Points

Closures - Challenge Task 3 of 3. How does this code know to return the first letter in a string?

This code works but it just seems like you'd have to use 'index' or 'characters.first' at some point in the function. The for loop seems like it will return all characters, not just the first character.

// Enter your code below
extension String {
    func modify(result: String -> String) -> String {
        return result(self)


func firstLetter(letter: String) -> String {
    for character in letter.characters {
        return "\(character)"
    return ""

let value = "Swift".modify(firstLetter)

1 Answer

Jennifer Nordell
Jennifer Nordell
Treehouse Teacher

The key here is to remember that once a return statement is hit the function exits. Since it starts a for loop it's going to go to the first character and then return it. And then the function exits. So it never makes it to the second letter :smiley: