How to insert row and section into UICollectionView at same time? - ios

Question

In UITableViewController I can insert row and section at the same time with this implementations:
func controllerWillChangeContent(controller: NSFetchedResultsController) {
self.tableView.beginUpdates()
}
func controller(controller: NSFetchedResultsController!, didChangeObject anObject: AnyObject!, atIndexPath indexPath: NSIndexPath!, forChangeType type: NSFetchedResultsChangeType, newIndexPath: NSIndexPath!) {
if controller == frc {
switch(type) {
case .Insert:
self.tableView.insertRowsAtIndexPaths([newIndexPath], withRowAnimation: .Fade)
case .Delete:
self.tableView.deleteRowsAtIndexPaths([indexPath], withRowAnimation: .Fade)
case .Update:
self.tableView.reloadRowsAtIndexPaths([indexPath], withRowAnimation: .None)
default:
break
}
}
}
func controller(controller: NSFetchedResultsController, didChangeSection sectionInfo: NSFetchedResultsSectionInfo, atIndex sectionIndex: Int, forChangeType type: NSFetchedResultsChangeType) {
switch(type) {
case .Insert:
self.tableView.insertSections(NSIndexSet(index: sectionIndex), withRowAnimation: .Fade)
case .Delete:
self.tableView.deleteSections(NSIndexSet(index: sectionIndex), withRowAnimation: .Fade)
default:
break
}
}
func controllerDidChangeContent(controller: NSFetchedResultsController) {
self.tableView.endUpdates()
}
What about UICollectionViewController? I haven't found alternative way to implement controllerWillChangeContent and controllerDidChangeContent.

Answer 1

collectionView works somewhat different than tableView, you need to use performBatchUpdates
var frc: NSFetchedResultsController?
var iip = [NSIndexPath]()
var dip = [NSIndexPath]()
var ins: NSIndexSet?
var des: NSIndexSet?
func controllerWillChangeContent(controller: NSFetchedResultsController) {
}
func controller(controller: NSFetchedResultsController!, didChangeObject anObject: AnyObject!, atIndexPath indexPath: NSIndexPath!, forChangeType type: NSFetchedResultsChangeType, newIndexPath: NSIndexPath!) {
if controller == frc {
switch(type) {
case .Insert:
iip.append(newIndexPath)
case .Delete:
dip.append(indexPath)
case .Update:
self.collectionView!.reloadItemsAtIndexPaths([indexPath])
default:
break
}
}
}
func controller(controller: NSFetchedResultsController, didChangeSection sectionInfo: NSFetchedResultsSectionInfo, atIndex sectionIndex: Int, forChangeType type: NSFetchedResultsChangeType) {
switch(type) {
case .Insert:
ins = NSIndexSet(index: sectionIndex)
case .Delete:
des = NSIndexSet(index: sectionIndex)
default:
break
}
}
func controllerDidChangeContent(controller: NSFetchedResultsController) {
self.collectionView!.performBatchUpdates({
self.collectionView!.insertItemsAtIndexPaths(self.iip)
self.collectionView!.deleteItemsAtIndexPaths(self.dip)
if self.ins != nil {
self.collectionView!.insertSections(self.ins!)
}
if self.des != nil {
self.collectionView!.deleteSections(self.des!)
}
}, completion: {completed in
self.iip.removeAll(keepCapacity: false)
self.dip.removeAll(keepCapacity: false)
self.ins = nil
self.des = nil
})
}

Answer 2

I was able to do this by checking to see if the section of the new index path is greater than the number of sections in the collection view, and then performing batch updates.
let indexPath = IndexPath()
// index path of item to be inserted
if indexPath.section > collectionView.numberOfSections - 1 {
collectionView.performBatchUpdates({
let set = IndexSet(integer: sectionIndex)
collectionView.insertSections(set)
self.collectionView.insertItems(at: [indexPath])
}, completion: nil)
} else {
collectionView.insertItems(at: [indexPath])
}