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 Error Handling in Swift Error Handling Throwing Errors

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

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
}