title: Avoiding registered object buildup (memleak) in NSManagedObjectContext
body: <p>I have a memory-intensive iOS app and I'm working on making sure that memory usage does not build up over time.  My app has a "main" context that lives for the lifetime of the app, with other smaller contexts being spawned occasionally for background tasks.</p>
  
  <p>One thing I have noticed is that NSManagedObjects appear to remain registered in the main context long-term and the only way to truly reclaim all the memory associated with pulling the objects from the DB is to call <code>[NSManagedObjectContext reset]</code>.</p>
  
  <p>This of course results in a nice drop in memory usage as all the registered objects from recently closed list views are properly ejected from memory, however it is annoying because you have just invalidated every object that was registered in that context that you still have a reference to (i.e. objects that are refered to by views that are still open), and you now need to re-fetch all the these objects from the database to avoid exceptions for accessing an invalidated object.</p>
  
  <p>Is this the only way of flushing out the registered object set from an NSManagedObjectContext, or is there a better way that successfully ejects all the registered objects you no longer have references to, but doesn't invalidate all the NSManagedObjects that are still alive?</p>