Question

I have an app that talks to the server to get some items (Item class) for current user and store it. So far so good.

I want to implement search, that essentially returns me a set of Item objects, but obviously I do not want to persist every search result there ever be. Another use case is that server API has different endpoints like recommendations/ new/ upcoming/ that return the same Item object, but in different context, so I would like to differentiate between them somehow.

My first thought was to use a throw-away managed context, load objects from API in there, do fetch and when user is done just destroy the context. Is it a good idea in general? It saves code, because most of my VCs already talk to core data.

Answer 1

Rather than throwing the whole wonderful infrastructure of Core Data away, you should leverage it to achieve your purpose.

• Add a timestamp attribute to your entity and use it to selectively display search results or even purge your store from old items.

• Add a category attribute to your entity and filter by category when searching.

Both can be achieved with an NSPredicate that you add to your NSFetchRequest. For example:

fetchRequest.predicate = [NSPredicate predicateWithFormat:
   @"timestamp > %@", [[NSDate date] dateByAddingTimeInterval:numberOfSeconds]];

or

fetchRequest.predicate = [NSPredicate predicateWithFormat:
  @"category = %@", @"new"];