The keyboard does not close when I tap on the screen

Question

I am implementing keyboard close as follows but it doesn't work.

extension SleepDiaryViewController: UITextFieldDelegate {
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        super.touchesBegan(touches, with: event)
        view.endEditing(true)
    }
}

Any ideas why this isn't working?