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◦ Whenever the current text changes, it calls the textField(_:shouldChangeCharactersIn:replacementString:) method and posts the textDidChangeNotification notification.
◦ It calls the textFieldShouldClear(_:) method when the user taps the built-in button to clear the text.
◦ It calls the textFieldShouldReturn(_:) method when the user taps the keyboard’s return button.