NSTableView Drag & Drop not working inside of an NSCollectionViewItem

I have a NSCollectionView and inside of the NSCollectionViewItems there is a label and a NSTableView. The NSTableViews are working properly EXCEPT for the drag & drop methods (tableView:writeRowsWithIndexes:toPasteboard:, tableView:validateDrop:proposedRow:proposedDro开发者_如何学编程pOperation:, and tableView:acceptDrop:row:dropOperation:). I have these working fine in other views, but I am not able to get them working inside of a NSCollectionViewItem. Is there a different trick that needs to be used for drag & drop for a NSTableView inside of a NSCollectionViewItem?