Swift错误警报操作执行Segue，但成功的操作不执行

Question

I am running into an issue with my signup controller where my error handler when a user leaves any text field blank fires an alert that once "OK" is clicked send the user to the next view controller that should appear only if the registration is successful. The opposite is occurring when a user successfully registers. My information is recorded, but no segue happens to the next view controller. How should I prevent this from happening?

import UIKit

class UserRegistrationViewController: UIViewController {

    @IBOutlet var usernameTextField: UITextField!

    @IBOutlet var emailTextField: UITextField!

    @IBOutlet var passwordTextField: UITextField!

    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view.
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }


    @IBAction func registerUser(sender: AnyObject) {

        var error = ""

        if usernameTextField.text == "" || emailTextField.text == "" || passwordTextField.text == "" {

            error = "Please enter a username, email and password"

        }


        if error != "" {

            var alert = UIAlertController(title: "Error In Form", message: error, preferredStyle: UIAlertControllerStyle.Alert)

            alert.addAction(UIAlertAction(title: "OK", style: .Default, handler: {
                action in

                self.dismissViewControllerAnimated(true, completion: nil)


            }))

            self.presentViewController(alert, animated: true, completion: nil)


        } else {

            var user = PFUser.currentUser()

            user.username = usernameTextField.text
            user.password = passwordTextField.text
            user.email = emailTextField.text

            user.saveInBackgroundWithBlock {
                (succeeded: Bool!, signupError: NSError!) -> Void in
                if signupError == nil {

                    println(user.username)
                    println(user.password)
                    println(user.email)




                    // Hooray! Let them use the app now.
                } else {
                    //let errorString = signupError.userInfo["error"] as NSString
                    // Show the errorString somewhere and let the user try again.

                    println("Error Registering")

                }
            }


        }


    }



    /*
    // MARK: - Navigation

    // In a storyboard-based application, you will often want to do a little preparation before navigation
    override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
        // Get the new view controller using segue.destinationViewController.
        // Pass the selected object to the new view controller.
    }
    */

}

Answer 1

I'm pretty sure that if a textfield is empty, it returns nil as opposed to and empty string. So simply checking for nil instead of an empty string should fix your issue. The change happened with iOS 7. Just to be sure you could check for both nil & "". Hope this helps

EDIT

If you wan't to you could do this:

if (usernameTextField.text == nil || usernameTextField.text.length > n) || ...

Where n is a number you specify. That way you can make sure that a user wouldn't sign up with a username or password that is too short. Depending on your requirements of course.

UPDATE:

When you create your user object you set it to PFUser.currentUser() which will be nil, because no one is logged in .

So all you need to do is to declare var user = PFUser() and it should work. Reference