How to get notified when scrollToRowAtIndexPath finishes animating

Question

This is a follow-up to How to get notified when a tableViewController finishes animating the push onto a nav stack.

In a tableView I want to deselect a

Answer 1

Implementing this in a Swift extension.

//strong ref required
private var lastDelegate : UITableViewScrollCompletionDelegate! = nil

private class UITableViewScrollCompletionDelegate : NSObject, UITableViewDelegate {
    let completion: () -> ()
    let oldDelegate : UITableViewDelegate?
    let targetOffset: CGPoint
    @objc private func scrollViewDidEndScrollingAnimation(scrollView: UIScrollView) {
        scrollView.delegate = oldDelegate
        completion()
        lastDelegate = nil
    }

    init(completion: () -> (), oldDelegate: UITableViewDelegate?, targetOffset: CGPoint) {
        self.completion = completion
        self.oldDelegate = oldDelegate
        self.targetOffset = targetOffset
        super.init()
        lastDelegate = self
    }
}

extension UITableView {
    func scrollToRowAtIndexPath(indexPath: NSIndexPath, atScrollPosition scrollPosition: UITableViewScrollPosition, animated: Bool, completion: () -> ()) {
        assert(lastDelegate == nil, "You're already scrolling.  Wait for the last completion before doing another one.")
        let originalOffset = self.contentOffset
        self.scrollToRowAtIndexPath(indexPath, atScrollPosition: scrollPosition, animated: false)

        if originalOffset.y == self.contentOffset.y { //already at the right position
            completion()
            return
        }
        else {
            let targetOffset = self.contentOffset
            self.setContentOffset(originalOffset, animated: false)
            self.delegate = UITableViewScrollCompletionDelegate(completion: completion, oldDelegate: self.delegate, targetOffset:targetOffset)
            self.scrollToRowAtIndexPath(indexPath, atScrollPosition: scrollPosition, animated: true)
        }
    }
}

This works for most cases although the TableView delegate is changed during the scroll, which may be undesired in some cases.