Is it possible to add observer to tableView.contentOffset?

Swift 5

tableContentObserver = table.observe(\UITableView.contentOffset, options: .new) { [weak self] table, change in
    self?.navigationItem.rightBarButtonItem?.title = "\(change.newValue)"
}

UITableView is a UIScrollView subclass so you can use the UIScrollViewDelegate method scrollViewDidScroll: to be notified when the view scrolled. Check the contentOffset of the scrollView in that method

contentOffset is a key path, so you can also observe its changes using KVO

[self.tableView addObserver:self forKeyPath:@"contentOffset" options:NSKeyValueObservingOptionNew | NSKeyValueObservingOptionOld context:nil];