Functionality for moving a textview Up or down in relation to the Keyboard

HandleKeyboard.swift

extension ChatController {
    func setupKeyboardObservers() {
        NotificationCenter.default.addObserver(self, selector: #selector(handleKeyboardWillShow(withNotification:)), name: .UIKeyboardWillShow, object: nil)
        NotificationCenter.default.addObserver(self, selector: #selector(handleKeyboardWillHide(withNotification:)), name: .UIKeyboardDidHide, object: nil)
    }
    @objc func handleKeyboardWillShow(withNotification notification: Notification) {
        let keyboardFrame = (notification.userInfo?[UIKeyboardFrameEndUserInfoKey] as AnyObject).cgRectValue
        let keyboardDuration = (notification.userInfo?[UIKeyboardAnimationDurationUserInfoKey] as AnyObject).doubleValue
        containerViewBottomAnchor?.constant = -(keyboardFrame?.height)! // bottomAnchor + constant
        UIView.animate(withDuration: keyboardDuration!) {
            self.view.layoutIfNeeded()
        }
    }
    @objc func handleKeyboardWillHide(withNotification notification: Notification) {
        let keyboardDuration = (notification.userInfo?[UIKeyboardAnimationDurationUserInfoKey] as AnyObject).doubleValue
        containerViewBottomAnchor?.constant = 0
        UIView.animate(withDuration: keyboardDuration!) {
            self.view.layoutIfNeeded()
        }
    }
}