UITableView+Animations.swift

extension UITableView {
    
    func animateSection<Element: Equatable>(section: Int, from:[Element], to: [Element], rowAnimation: UITableViewRowAnimation = .Top) {
        assert(from.containsUniqueElements() && to.containsUniqueElements(), "\(#function) can only be used if all elements in the collection are unique.")
        
        func path(index: Int) -> NSIndexPath {
            return NSIndexPath(forRow: index, inSection: section)
        }
        
        // Find indexes in the old array that should be deleted
        let deletedIndices = from.enumerate().flatMap { index, oldElement in
            return to.contains(oldElement) ? nil : index
        }
        
        // Find indexes of new objects inserted into the destination array
        let insertedIndices = to.enumerate().flatMap { index, newElement in
            return from.contains(newElement) ? nil : index
        }
        
        // Find indexes in the source array of elements that have not been deleted
        let retainedIndices = from.enumerate().flatMap { index, oldElement in
            return to.contains(oldElement) ? index : nil
        }
        
        // Find the indexes in the source and destination arrays of any moved elements.
        let movements: [(Int, Int)] = retainedIndices.flatMap { (movedFromIndex) -> (Int, Int)? in
            let movement = (movedFromIndex, to.indexOf(from[movedFromIndex])!)
            return (movement.0 != movement.1) ? movement : nil
        }
        
        beginUpdates()
        deleteRowsAtIndexPaths(deletedIndices.map { path($0) }, withRowAnimation: rowAnimation)
        insertRowsAtIndexPaths(insertedIndices.map { path($0) }, withRowAnimation: rowAnimation)
        for movement in movements {
            moveRowAtIndexPath(path(movement.0), toIndexPath: path(movement.1))
        }
        endUpdates()
    }
    
}