title: NSFetchedResultsController sections localized sorted
body: <p>How could I use the NSFetchedResultsController with translated sort key and sectionKeyPath?</p>
  
  <p>Problem: I have ID in the property "type" in the database like typeA, typeB, typeC,... and not the value directly because it should be localized. In English typeA=Bird, typeB=Cat, typeC=Dog in German it would be Vogel, Katze, Hund.</p>
  
  <p>With a NSFetchedResultController with sort key and sectionKeyPath on "type" I receive the order and sections
  - typeA
  - typeB
  - typeC</p>
  
  <p>Next I translate for display and everything is fine in English:
  - Bird
  - Cat
  - Dog</p>
  
  <p>Now I switch to German and receive a wrong sort order
  - Vogel
  - Katze
  - Hund</p>
  
  <p>because it still sorts by typeA, typeB, typeC</p>
  
  <p>So I'm looking for a way to localize the sort for the NSFetchedResultsController.</p>
  
  <p>I tried the transient property approach, but this doesn't work for the sort key because the sort key need to be in the entity.</p>
  
  <p>I have no other idea. But I can't believe that's not possible to use NSFetchedResultsController on a derived attribute required for localization?</p>
  
  <p>There are related discussions like <a href="https://stackoverflow.com/questions/1384345/using-custom-sections-with-nsfetchedresultscontroller">Using custom sections with NSFetchedResultsController?</a> but the difference is that the custom section names and the sort key have probably the same order. Not in my case and this is the main difference. </p>
  
  <p>At the end I would need a sort order for the necessary NSSortDescriptor on a derived attribute, I guess. This sort order has also to serve for the sectionKeyPath.</p>
  
  <p>Thanks for any hint.</p>