UITextFieldDelegate not working for childViewController Swift

Question

I added a SecondViewController as a child after pressing a button. The code below is the button action inside MainViewController.

@IBAction func btnPressed(_ sender: Any) {    
    addChildViewController(SecondViewController())

    view.superview?.addSubview(SecondViewController().view)

    SecondViewController().view.frame = (view.superview?.bounds)!
                SecondViewController().view.autoresizingMask = [.flexibleWidth, .flexibleHeight]

    SecondViewController().didMove(toParentViewController: self)
}

Inside SecondViewController, I set UITextFieldDelegate like this

class SecondViewController: UIViewController, UITextFieldDelegate {

and I set textField delegate with view controller on my xib. Even tried with myTextField.delegate = self. This is my shouldChangeCharactersIn range

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
        print("While entering the characters this method gets called")
        return true;
    }

But that method never get called.

Answer 1

What you are doing is creating 5 different instances of SecondViewController - you are doing that by calling initializer (SecondViewController()) in each line

@IBAction func btnPressed(_ sender: Any) {    
    addChildViewController(SecondViewController()) // first instance created

    view.superview?.addSubview(SecondViewController().view) // second instance created

    SecondViewController().view.frame = (view.superview?.bounds)! // third instance created
    SecondViewController().view.autoresizingMask = [.flexibleWidth, .flexibleHeight] // fourth instance created

    SecondViewController().didMove(toParentViewController: self) // fifth instance created
}

Do instead

@IBAction func btnPressed(_ sender: Any) {   
    let secondViewController = SecondViewController()

    addChildViewController(secondViewController)
    view.superview?.addSubview(secondViewController.view)
    secondViewController.view.frame = (view.superview?.bounds)!
    secondViewController.view.autoresizingMask = [.flexibleWidth, .flexibleHeight]
    secondViewController.didMove(toParentViewController: self)
}