The best way to implement the UICollectionViewDataSource protocol?

I have theoretical question.

Currently my app is using UICollectionView as a way to display objects list. UIViewController, that contains UICollectionView as subview, implements UICollectionViewDelegate protocol and acts as delegate and datasource. Datasource uses NSFetchedResultsController to provide data;

In my opinion this is not the best way to implement datasource, and implementing it in separate class looks way better idea. But the issue it that datasource depends on search parameters in UITextField, and some other buttons selections, so every time when user types text into search field or press the any of "sorting" buttons I should update datasource (in particular fetchRequest in NSFetchedResultsController).

So, finally, my question: Is there any "best practices" of implementing datasources that depends on external parameters? Should I create separate class for datasource of leave it the way it is now? If implementing datasource as separate class - should I create datasourcedelegate for calling self-made delegate methods on delegate when datasource was updated or there is some other workarounds for this problem (I'm not considering using notifications on datasource update because as for me notifications mechanism is more global solution then I need here)?

I'm not looking for the fastest way, I just want to find out the rightest theoretical way of implementation.

Thank you all in advance :)

I personally implemented a concrete NSObject derived class, that implements UICollectionViewDataSource as well as NSFetchedResultsControllerDelegate that practically translates the fetched results controller events (object inserted, updated, deleted) to collection view events (insert, update or delete cells). You can find examples on how to do this, I took mine from here but I implemented it as a separate class instead of a category over collection view. I found my class highly reusable, in practice I use it in all of my projects where there is a need to visualize managed objects in a collection view. A similar class can be implemented also for UITableViewDataSource.

If you need to update the fetch request with the search predicate, I would subclass your newly created DataSource class, and add the logic to update the fetch request right there. Say, you add a -(void)updateSearchFilterWithText:(NSString*)text method where you add the logic to update the fetch request of the fetched results controller. Don't forget to perform fetch again afterwards and call a reloadData on the collection view!

With this architecture the view controller owns this dataSource object. Every time the user updates one of your filtering text field (or other widget), the view controller calls the updateSearchFilterWithText: of your data source object and the rest of the work is done by this later.