Get UITableView contentSize after insert/delete rows

Question

I want to achieve tableViewCell is selected then insert some rows. Select again then delete these rows. The method like below:

func animateRows(tableView: UITableView, insert: Bool, indexPaths: [IndexPath]) {
        tableView.beginUpdates()
        if (insert) {
            tableView.insertRows(at: indexPaths, with: .fade)
        } else {
            tableView.deleteRows(at: indexPaths, with: .fade)
        }
        tableView.endUpdates()
        print(tableView.contentSize)
        tableView.reloadData()
        print(tableView.contentSize)
    }

This method works well. I want to get the contentSize after insert or delete action ends. Then reset the tableView's content size. But the only way i found is after call tableView.reloadData() the contentSize was updated. But feel not proper. Any other good solutions?

EDIT:

What are you doing with contentSize of a UITableView anyways?

I need the contentSize to make the tableView height fit the content. Actually my tableView is one subView of UIScrollView. I need the tableView show all rows all the time. Then layout scrollView contentSize properly.