Swift believes non-nil value is actually nil - ios

Question

I have two text boxes, passwordTextField and emailTextField. Values are entered into each. When I hit print, the values print in the console.
However, I am receiving the following error when using the next function to populate a text box on the next view controller.
Note
This was working not a few hours ago and I have changed nothing, so I am unsure how or why this now does not work.
#IBOutlet weak var passwordTextField: UITextField!
#IBOutlet weak var emailTextField: UITextField!
#IBOutlet weak var registerButton: UIButton!
#IBAction func registerButtonPressed(_ sender: Any) {
let next = self.storyboard?.instantiateViewController(withIdentifier: "ABC") as! ABCViewController
self.present(next, animated: true,completion: nil)
let nameText = self.emailTextField.text!
let passwordText = self.passwordTextField.text!
print(nameText) // prints email
print(passwordText) // prints password
next.username.text = nameText // prints error: Unexpectedly found nil while implicitly unwrapping an Optional value
next.password.text = passwordText
}
Unexpectedly found nil while implicitly unwrapping an Optional value.
But non-nil values are displaying when printing out.

Answer 1

The code is unreliable because it's not guaranteed that the view in the second controller is loaded right after the present line.
All outlets are nil until the view is available.
Declare temporary properties in ABCViewController and populate the text fields in viewDidLoad
class ABCViewController : UIViewController {
#IBOutlet weak var username: UITextField!
#IBOutlet weak var password: UITextField!
var tempName = ""
var tempPassword = ""
// .....
func viewDidLoad() {
super.viewDidLoad()
username.text = self.tempName
password.text = self.tempPassword
}
}
In registerButtonPressed assign the values to the temporary properties and present the controller, nothing else.
#IBAction func registerButtonPressed(_ sender: Any) {
let next = self.storyboard?.instantiateViewController(withIdentifier: "ABC") as! ABCViewController
next.tempName = self.emailTextField.text!
next.tempPassword = self.passwordTextField.text!
self.present(next, animated: true,completion: nil)
}