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 2 Extensions and Protocols Extending a Native Type

Posted by anthony fontes
anthony fontes
12,405 Points

Stuck on string extension challenge

don't know how to make the method add to a string

types.swift 
// Enter your code below
 extension String {

    func add(val: Int) -> Int {
        return self + add(val) ???
    }
 }

1 Answer

rh12
rh12
4,407 Points

Good start so far.

You want to try and convert "self" (which is a String) to a Int first before adding it to the provided value. If "self" cannot be converted to a number, then you can return a nil.

extension String {
  func add(value: Int) -> Int? {
    if let stringAsNumber = Int(self) {
      return stringAsNumber + value
    } else {
      return nil
    }
  }
}