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

Swift 4:

As per:

https://developer.apple.com/documentation/foundation/nserror

if you don't want to define a custom exception, you could use a standard NSError object as follows:

import Foundation

do {
  throw NSError(domain: "my error domain", code: 42, userInfo: ["ui1":12, "ui2":"val2"] ) 
}
catch let error as NSError {
  print("Caught NSError: \(error.localizedDescription), \(error.domain), \(error.code)")
  let uis = error.userInfo 
  print("\tUser info:")
  for (key,value) in uis {
    print("\t\tkey=\(key), value=\(value)")
  }
}

Prints:

Caught NSError: The operation could not be completed, my error domain, 42
    User info:
        key=ui1, value=12
        key=ui2, value=val2

This allows you to provide a custom string (the error domain), plus a numeric code and a dictionary with all the additional data you need, of any type.

N.B.: this was tested on OS=Linux (Ubuntu 16.04 LTS).