title: Using Core Data as a local cache for data retrieved from remote web services
body: <p>My project has a need to cache on the iOS device data retrieved from a remote web service. The idea is the view controller will ask the cache for all the document objects it has, for example, and in the background will request a refresh from the web service, returning to the view controller any new document objects it received. I'm wondering whether it's possible for the view controllers to use a NSFetchedResultsController that retrieves whatever objects matching the criteria it can find locally in the database, and also asynchronously asks for data refreshes from the web service in the background. In doing so, the NSFetchedResultsController would update the database and of course trigger the didChangeObject method of the FetchedResultsController delegate so the views can update accordingly. Does that sound reasonable? Do you have any suggestions for implementing such a thing?</p>