KeyboardNotification.swift

extension ViewController {
    
    private func setupKeyboardNotifications() {
        NotificationCenter.default.addObserver(self,
                                               selector: #selector(keyboardWillShow(_:)),
                                               name: UIResponder.keyboardWillShowNotification,
                                               object: nil)

        NotificationCenter.default.addObserver(self,
                                               selector: #selector(keyboardWillHide(_:)),
                                               name: UIResponder.keyboardWillHideNotification,
                                               object: nil)
    }
    
    @objc
    private func keyboardWillShow(_ sender: Notification) {
        guard let info = sender.userInfo,
            let frame = (info[UIResponder.keyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValue else {
                return
        }
                
        self.bottomConstraint.constant = frame.size.height
        UIView.animate(withDuration: 0.3) {
            self.view.layoutIfNeeded()
        }
    }
    
    @objc
    private func keyboardWillHide(_ sender: Notification) {
        self.bottomConstraint.constant = 0
        self.view.layoutIfNeeded()
    }
    
}