ViewController segue and login

Question

I'm new to Swift (and programming in general). I'm having some difficulties in Xcode with the login feature. What I want is that the user should be logged in if no errors was returned and the user should be sent to another controller. I've read some of the documentation from Apple and the performSegueWithIdentifier (and of course some questions asked here), but it still does not work when I use a segue with push or modal that are given an identifier. Either the app crashes, or the user is sent to my UITabBarController even if the credentials was incorrect.

This is my LogInViewController.swift:

@IBAction func loginAction(sender: AnyObject)
{
    if self.emailField.text == "" || self.passwordField.text == ""
    {
        let alertController = UIAlertController(title: "Oops!", message: "Please enter an email and password.", preferredStyle: .Alert)

        let defaultAction = UIAlertAction(title: "OK", style: .Cancel, handler: nil)
        alertController.addAction(defaultAction)

        self.presentViewController(alertController, animated: true, completion: nil)
    }
    else
    {
        FIRAuth.auth()?.signInWithEmail(self.emailField.text!, password: self.passwordField.text!) { (user, error) in

            if error == nil
            {
                self.emailField.text = ""
                self.passwordField.text = ""
            }
            else
            {
                let alertController = UIAlertController(title: "Oops!", message: error?.localizedDescription, preferredStyle: .Alert)

              let defaultAction = UIAlertAction(title: "OK", style: .Cancel, handler: nil)
                alertController.addAction(defaultAction)

                self.presentViewController(alertController, animated: true, completion: nil)
            }
             // User Logged in
                self.performSegueWithIdentifier("LoggedIn", sender: self)
        }
    }
}

The error I get in the console:

2016-09-04 14:55:30.019 DrinkApp[37777:1006336] *** Terminating app due to uncaught exception 'NSGenericException', reason: 'Could not find a navigation controller for segue 'LoggedIn'. Push segues can only be used when the source controller is managed by an instance of UINavigationController.'

Answer 1

There are two main ways to send a user to another View Controller. The first is performSegueWithIdentifier. Here's how you would go about using that:

First of all, control-drag from the yellow circle of the original VC to the target VC in the interface builder.

Next, click on the 'segue arrow' that appears between the two View Controllers.

In the identifier field, type in mySegue.

Next, go back to your code. When you reach the sign in section, add the following code:

self.performSegueWithIdentifier("mySegue", sender: nil)

The second method is a bit more advanced. Here's how that would work:

First, click on the yellow circle of the destination VC. Click on the newspaper, then call the storyboard ID myVC.

Make sure to click on Storyboard ID

Go back to the same part of the code and copy and paste this code:

    let storyboard: UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
    let initViewController: UIViewController = storyboard.instantiateViewControllerWithIdentifier("myVC") as UIViewController
    self.presentViewController(initViewController, animated: true, completion: nil)
    

Comment down below if you have any questions. Good luck!