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 Intermediate Swift Extensions and Protocols Extending a Native Type

Richard Sun
Richard Sun
11,257 Points

Why does Treehouse say that I haven't added an add method?

Treehouse says that I haven't added an Add Method and one that returns an int even though I have. What is wrong?

types.swift
// Enter your code below
extension String {
    func add(value: Int) -> Int {
        do {
            let num = Int(self)
            return num! + value
        } catch {
            return nil
        }
    }
}

1 Answer

Jeff McDivitt
Jeff McDivitt
23,970 Points

The easiest way to handle this is to make the return Int an optional and use a guard statement

    func add(value: Int) -> Int?{
        guard let convertedNumber = Int(self) else{
            return nil
        }

        return convertedNumber + value
    }

}