When does UITableView content size update with row insert/delete animation

Question

I am curious when the UITableView\'s content size is updated after doing an insert/delete animation call. I figured it would be like most [UIView animation...] blocks in tha

Answer 1

It looks like sizeThatFits() can expose the height of a new contentSize that's pending. You can then assign that pending size to have it resolve early for scroll animations.

With something like this:

extension UIScrollView {

    var pendingContentSize: CGSize {
        var tallSize = contentSize
        tallSize.height = .greatestFiniteMagnitude
        return sizeThatFits(tallSize)
    }

    func scrollToBottom(animated: Bool) {
        contentSize = pendingContentSize
        let contentRect = CGRect(origin: .zero, size: contentSize)
        let (bottomSlice, _) = contentRect.divided(atDistance: 1, from: .maxYEdge)
        guard !bottomSlice.isEmpty else { return }
        scrollRectToVisible(bottomSlice, animated: animated)
    }

}

I'm able to write view controller code like this:

tableView.insertRows(at: [newIndexPath], with: .none)
tableView.scrollToBottom(animated: true)

and have the table scroll all the way to the bottom (using the new content size) instead of it scrolling down to the 2nd-to-last row (using the old content size).