Invalid Update: Invalid Number of Items on Uicollectionview

Invalid update: invalid number of items on UICollectionView

It's a bug with using insertItemsAtIndexPaths on an empty UICollectionView. Just do this:

if (self.birthdays.count == 1) {
    [self.collectionView reloadData];
} else {
    [self.collectionView insertItemsAtIndexPaths:@[[NSIndexPath indexPathForItem:   (self.birthdays.count -1) inSection:0]]];
}

(Can't believe this is still broken in iOS8.)

Invalid update: invalid number of items in section 0 in my collection view

You never update your data model. Beside deleting the file and telling the collection view that an item has been deleted, you also need to update the model used by the collection view. This means you need to update numberOfRecordings (before calling myCollectionView.deleteItems(at: [indexPath]).

How to solve the error Invalid update: incorrect number of items in section 0 in the collection View on iOS12?

Where are the batch updates (plural)?

You don't need performBatchUpdates, the method is only useful for multiple simultaneous updates. Delete the card in the database, on success remove the card from the data source array and delete the item – animated – in the collection view.

My suggestion assumes that the current index path is available which itemIndex derives from

item = self.cards[itemIndex]

self.db.collection(K.FStore.collectionName!).document((item?.idCard)!).delete() { err in
   if let error = err {
      print("An error occurred", error)
   } else {
      self.cards.remove(at: itemIndex)
      self.collectionView.deleteItems(at: [indexPath])
   }
}

Invalid update: invalid number of items in section 0.

The call to insertItems(at:) and deleteItems(at:) must be accompanied with change in the datasource as well.

So, before calling these APIs, you would want to change your datasource, i.e. add objects into it before calling insertItems and remove objects from it before calling deleteItems

Invalid update: invalid number of rows in section 0 with NSFetchedResultsController

Doc states:

controller(_:didChange:at:for:newIndexPath:)

indexPath

The index path of the changed object (this value is nil for
insertions).

So, you should change the code like this:

    func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange anObject: Any, at indexPath: IndexPath?, for type: NSFetchedResultsChangeType, newIndexPath: IndexPath?) {
      switch type {
            case .update:
                if let indexPath = indexPath {
                   tableView.reloadRows(at: [indexPath], with: .none)
              }
            case .move:
               if let indexPath = indexPath {
                  tableView.moveRow(at: indexPath, to: newIndexPath)
               }
           case .delete:
                if let indexPath = indexPath {
                   tableView.deleteRows(at: [indexPath], with: .none)
                   tableView.reloadData()   // << May be needed ?
               }
           case .insert:
                if let newIndexPath = newIndexPath {
                   tableView.insertRows(at: [newIndexPath], with: .none)
                   tableView.reloadData()   // << May be needed ?
               }
           default:
                tableView.reloadData()
            }
    }
}

Invalid update: invalid number of sections in UITableView

When you remove the last row from a section, you need to let the table view that the whole section has been removed.

You can do this by implementing

func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, 
           didChange sectionInfo: NSFetchedResultsSectionInfo, 
      atSectionIndex sectionIndex: Int, 
                 for type: NSFetchedResultsChangeType) {

    let section = IndexSet(integer: sectionIndex)

    switch type {
        case .delete:
            tableView.deleteSections(section, with: .automatic)
        case .insert:
            tableView.insertSections(section, with: .automatic)
    }
}

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