从UICollection删除项目但出现“数组索引超出范围”错误

Question

I'm using Parse as a backend and loading items into a UICollectionView. Everything works great but I can't seem to properly delete certain ranges of items. Here's my delete function:

func deleteButtonTapped() {
  let indexPaths = collectionView!.indexPathsForSelectedItems()!

  self.collectionView!.performBatchUpdates({
    for index in indexPaths {
      self.tasks[index.item].deleteInBackground()
      self.tasks.removeAtIndex(index.item)
    }
  }, completion: nil)

  self.collectionView!.deleteItemsAtIndexPaths(indexPaths)
}

I get the error: fatal error: Array index out of range I think this is because as the for loop cycles it loses an item but maintains the original count. I checked to make sure self.tasks and indexPaths returns what I expect. Not sure what else to try. How can I refactor this? Any help or direction would be much appreciated. Thanks!

Answer 1

Try to put the self.collectionView!.deleteItemsAtIndexPaths(indexPaths) inside the completion handler of performBatchUpdates .

EDIT

It looks like you are attempting to remove an item from self.tasks while accessing it. Say for example your tasks have 5 items [A,B,C,D,E] and you select to delete D & E. on the first iteration you delete item at index 3 (ie D). Now tasks have 4 items [A,B,C,E]. On the next iteration when you try to access item at index 4, which before the previous delete pointed to E, you'll get index out of bound error.