NSBlockOperations causing memory leaks, and causing deinit never gets called [swift]

Question

var blockOperations = [NSBlockOperation]()
func controller(controller: NSFetchedResultsController, didChangeObject anObject: AnyObject, atIndexPath indexPath: NSIndexPath?, forChangeType type: NSFetchedResultsChangeType, newIndexPath: NSIndexPath?) {

    if type == .Insert {
        blockOperations.append(NSBlockOperation(block: {
            self.collectionView?.insertItemsAtIndexPaths([newIndexPath!])

        }))
    }
}
    func controllerDidChangeContent(controller: NSFetchedResultsController) {
    collectionView?.performBatchUpdates({
        for operation in self.blockOperations {
            operation.start()

        }
        }, completion: { (completed) in
           print("completed")
    })

}

This is my code for inserting messages into my collection view.

I need block operations so that when a message is delayed it can be inserted in a block matter.

The problem is every time I dismiss the viewController the print("completed") duplicates. which means that i have a memory leak.

And deinit never gets called unless I remove block operations, how can I release the block operation when I leave the viewController?