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 Closures in Swift First Class Functions Higher Order Functions

can anyone help I am stuck with intermediate swift - closures - functions Challenge 1 of 3

Challenge Task 1 of 3

In an extension to the String type, declare a function named transform. The function should accept as an argument another function of type (String) -> String. For this argument, let's omit the external label. The transform function should also return a String.

In the body of the method, return the result of applying the function argument to self.

I ended up with this (but its wrong):

extension String { func transform(argument: (String) -> String) -> String { return argument(self) } }

extension String {
  func transform(argument: (String) -> String) -> String {
    return argument(self)

2 Answers

It looks like the only part you are missing is the let's omit the external label.

In Swift you can omit labels by adding a _ before your argument, so:

func transform(_ argument: (String) -> String) -> String { ... }

This allows you to not need to specify the label name when calling the method: transform("someString") instead of transform(argument: "someString")

Thanks for the help Joe