title: How to get objects after CoreData Context merged
body: <p>I tried to save data and merge with CoreData and multi-thread for iPhone app.
  But I can't get managed objects in the main thread after merging.</p>
  
  <p>I wrote code just like this:</p>
  
  <pre><code>[managedObjectContext performSelectorOnMainThread:@selector(mergeChangesFromContextDidSaveNotification:)
                                         withObject:notification
                                      waitUntilDone:YES];
  
  [self performSelectorOnMainThread:@selector(didMerged:) withObject:objectIds waitUntilDone:YES];
  </code></pre>
  
  <p>So I tried to pass objectIds to get NSManagedObject instances in the main thread which were generated in another thread. At first I tried "objectWithId" method but it generated fault objects. Then I tried "existingObjectWithID" method but it generated objects partly and others were nil with following Error:</p>
  
  <pre><code>[Error] Error Domain=NSCocoaErrorDomain Code=133000 "Operation could not be completed. (Cocoa error 133000.)"
  </code></pre>
  
  <p>What is wrong? Is there any way how to retrieve all objects by objectIds after merging in another thread?</p>
  
  <p>Thank you.</p>