UITableViewCell animation in only one direction - ios

Question

I want to animate UITableViewCell only in one direction [down direction]
my code:
func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {
cell.alpha = 0
let transform = CATransform3DTranslate(CATransform3DIdentity, 0, 200 , 0)
cell.layer.transform = transform
UIView.animate(withDuration: 0.5, delay: 0, usingSpringWithDamping: 1, initialSpringVelocity: 1, options: .curveEaseOut, animations: {
cell.alpha = 1
cell.layer.transform = CATransform3DIdentity
})
}
how can i stop that animation [don't perform animation] while user scroll upside?
thanks!!

Answer 1

If you have just one section, you can simply compare the current indexPath with the one that was presented as last, and animate only when the new indexPath.row is greater:
fileprivate var lastIndexPath: IndexPath = IndexPath(row: -1, section: 0)
func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {
// perform animation only when new indexPath.row is greater then the last presented
if lastIndexPath.row < indexPath.row {
cell.alpha = 0
let transform = CATransform3DTranslate(CATransform3DIdentity, 0, 200 , 0)
cell.layer.transform = transform
UIView.animate(withDuration: 0.5, delay: 0, usingSpringWithDamping: 1, initialSpringVelocity: 1, options: .curveEaseOut, animations: {
cell.alpha = 1
cell.layer.transform = CATransform3DIdentity
})
}
lastIndexPath = indexPath
}
In case of multiple sections, the approach is the same, just the comparison would be a bit more complicated, because you will have to take sections into account. So instead of:
if lastIndexPath.row < indexPath.row {
You would have to use something like:
if lastIndexPath.section < indexPath.section ||
(lastIndexPath.section == indexPath.section && lastIndexPath.row < indexPath.row) {