xcode how to know which textfield is selected

class ViewController : UIViewController, UITextFieldDelegate {

   var activeTextField = UITextField()

   // Assign the newly active text field to your activeTextField variable
   func textFieldDidBeginEditing(textField: UITextField) {

        self.activeTextField = textField

   // Call activeTextField whenever you need to
   func anotherMethod() {

       // self.activeTextField.text is an optional, we safely unwrap it here
       if let activeTextFieldText = self.activeTextField.text {
             print("Active text field's text: \(activeTextFieldText)")

       print("Active text field is empty")

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