Class method on PFUser subclass that throws

gistfile1.txt

// In this example, we will create a class method for our PFUser subclass
// The method will register a new user, but throw certain error types for us to exhaustively handle 

// First, we define our errors as an enum that conforms to ErrorType
// Here we anticipate common error cases 
enum SignUpError: ErrorType {
    case EmptyFields
    case TooLong
    case TooShort
}

//Here is our class in which we define the method we will later call
class User: PFUser {

    // This class method will create a new user, taking in the username and password as parameters
    // Notice we add "throws" at the end of the method declaration
    // And within the method, we guard against the various cases. And throw the appropriate error type within them
    class func registerNewUser(username : String!, password : String!, completed:(error : NSError!) -> Void) throws
    {
        guard username.characters.count > 0 || password.characters.count > 0 else {
            throw SignUpError.EmptyFields
        }
        
        guard password.characters.count > 6 else {
            throw SignUpError.TooShort
        }
        
        guard password.characters.count < 16 else {
            throw SignUpError.TooLong
        }

        let newUser = User()
        newUser.username = username.lowercaseString
        newUser.password = password.lowercaseString

        newUser.signUpInBackgroundWithBlock { (succeeded, signUpError) -> Void in
            completed(error: signUpError)
        }
    }
}

//Then, (for example) in a view-controller where we call that method we can react to the error types being thrown:
class SignUpViewController: UIViewController {

    @IBOutlet var usernameTextField: UITextField!
    @IBOutlet var passwordTextField: UITextField!

    // Within a "do", we call our custom class method that "throws" using "try"
    // Following the "do", we "catch" the various errorTypes (of our enum) that can be thrown
    @IBAction func onSignUpButtonTapped(sender: UIButton) {
        do {
            try User.registerNewUser(usernameTextField.text, password: passwordTextField.text, completed: { (error) -> Void in
                self.dismissViewControllerAnimated(true, completion: nil)
            })
        } catch SignUpError.EmptyFields {
            print("empty fields")
        } catch SignUpError.TooShort {
            print("too short")
        } catch SignUpError.TooLong {
            print("too long")
        } catch {
            print("something else went wrong")
        }
    }
}