Simplest way to throw an error/exception with a custom message in Swift 2?

Question

I want to do something in Swift 2 that I\'m used to doing in multiple other languages: throw a runtime exception with a custom message. For example (in Java):

Answer 1

Throwing code should make clear whether the error message is appropriate for display to end users or is only intended for developer debugging. To indicate a description is displayable to the user, I use a struct DisplayableError that implements the LocalizedError protocol.

struct DisplayableError: Error, LocalizedError {
    let errorDescription: String?

    init(_ description: String) {
        errorDescription = description
    }
}

Usage for throwing:

throw DisplayableError("Out of pixie dust.")

Usage for display:

let messageToDisplay = error.localizedDescription