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 Error Handling in Swift Error Handling Throwing Errors

Posted by erinkrentz
erinkrentz
8,839 Points

Error Handling Challenge Task 2 What is the single member? How can I have an error for invalidData if I have no data?

Here is what I am trying:

enum BookError: Error { case incorrectTitle }

func lend(book: String?) throws { guard let book = book else { throw BookError.incorrectTitle } }

error.swift 
enum BookError: Error {
  case incorrectTitle
}

func lend(book: String?) throws  {
    guard let book = book else {
        throw BookError.incorrectTitle
    }
}

1 Answer

Nichlas Kondrup
Nichlas Kondrup
17,748 Points
Nichlas Kondrup
Nichlas Kondrup
17,748 Points

The function shouldn't have any parameters. The function should simply throw the incorrectTitle error. The incorrectTitle error is referred as the single member because it is the only member in the enum.

enum BookError: Error {
  case incorrectTitle
}

func lend() throws {
  throw BookError.incorrectTitle
}