associated_value_success_enums.swift

// IMPLEMENTATION
enum LookupError: ErrorType {
  case InvalidName
  case NullData
}

enum UserResult {
  case Success(String)
  case Error(LookupError)
}

func findUserStatus(name: String) -> UserResult {
  guard let userStats = users[name] else {
    return .Error(InvalidName)
  }
  return .Success(userStats)
}

// USAGE
switch findUserStatus("Stevie Wonder") {
  case let .Success(stats):
    print("Stevie Wonder's Stats: \(stats)")
  case let .Error(error):
    print("Error: \(error));
}