var observation: NSKeyValueObservation?
override func viewDidLoad() {
super.viewDidLoad()
self.observation = self.downView.observe(\UIView.isHidden, options: [.new]) { (_, change) in
if let hidden = change.newValue {
self.collectionTableView.contentInset = UIEdgeInsets(top: 0, left: 0, bottom: hidden ? 0 : self.downView.frame.height, right: 0)
}
}
}