title: core data child/parent save exception
body: <p>I got crash (probably while parent moc saved:</p>
  
  <p>this is how moc's created (parent):</p>
  
  <pre><code>   if (_managedObjectContextInMemoryForDynamicInformation) return _managedObjectContextInMemoryForDynamicInformation;
      NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinatorInMemoryForDynamicInformation];
      if (!coordinator) {
          NSMutableDictionary *dict = [NSMutableDictionary dictionary];
          [dict setValue:@"Failed to initialize the store" forKey:NSLocalizedDescriptionKey];
          [dict setValue:@"There was an error building up the data file." forKey:NSLocalizedFailureReasonErrorKey];
          NSError *error = [NSError errorWithDomain:@"YOUR_ERROR_DOMAIN" code:9999 userInfo:dict];
          [[NSApplication sharedApplication] presentError:error];
          return nil;
      }
      _managedObjectContextInMemoryForDynamicInformation = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];
      [_managedObjectContextInMemoryForDynamicInformation setPersistentStoreCoordinator:coordinator];
      [_managedObjectContextInMemoryForDynamicInformation setUndoManager:nil];
      return _managedObjectContextInMemoryForDynamicInformation;
  </code></pre>
  
  <p>child:</p>
  
  <pre><code>    AppDelegate *delegateMain = (AppDelegate *)[[NSApplication sharedApplication] delegate];
      _mocInMemoryForDynamicInformation = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType];
      [_mocInMemoryForDynamicInformation setUndoManager:nil];
      _mocInMemoryForDynamicInformation.parentContext = delegateMain.managedObjectContextInMemoryForDynamicInformation;
  </code></pre>
  
  <p>this is how i save:</p>
  
  <pre><code>-(void) finalSaveMocInMemoryForDynamicInformation;
  {
      [_mocInMemoryForDynamicInformation performBlock:^{
          // do something that takes some time asynchronously using the temp context
  
          // push to parent
          NSError *error;
          if ([_mocInMemoryForDynamicInformation save:&amp;error])
          {
              AppDelegate *delegateMain = (AppDelegate *)[[NSApplication sharedApplication] delegate];
  
              // save parent to disk asynchronously
              [delegateMain.managedObjectContextInMemoryForDynamicInformation performBlock:^{
                  @try {
                      NSError *error;
                      if (![delegateMain.managedObjectContextInMemoryForDynamicInformation save:&amp;error])
                      {
                          [self logError:error];
                      }
                  }
                  @catch (NSException *exception) {
                      NSLog(@"ERROR:%@:%@ exception-&gt;%@ inside managedObjectContextInMemoryForDynamicInformation",[self class], NSStringFromSelector(_cmd),exception);
                      //[[NSNotificationCenter defaultCenter] removeObserver:self name:NSManagedObjectContextDidSaveNotification object:moc];
  
                      return ;
                  }
  
              }];
          } else [self logError:error];
      }];
  }
  </code></pre>
  
  <blockquote>
    <p>Application Specific Information:
    <em>*</em> Terminating app due to uncaught exception 'NSObjectInaccessibleException', reason: 'CoreData could not fulfill a
    fault for '0x7fd8a71d87a0
    ''
    abort() called terminate called throwing an exception</p>
    
    <p>Application Specific Backtrace 1: 0   CoreFoundation<br>
    0x00007fff86e6f0a6 __exceptionPreprocess + 198 1   libobjc.A.dylib<br>
    0x00007fff849353f0 objc_exception_throw + 43 2   CoreData<br>
    0x00007fff8737eec4 _PFFaultHandlerLookupRow + 1348 3   CoreData<br>
    0x00007fff8737e61f _PF_FulfillDeferredFault + 239 4   CoreData<br>
    0x00007fff873892cd _PF_ManagedObject_WillChangeValueForKeyIndex + 77 5
    CoreData                            0x00007fff8738cc51
    _sharedIMPL_setvfk_core + 129 6   CoreData                            0x00007fff873a4eaa -[NSManagedObject(_NSInternalMethods)
    _didChangeValue:forRelationship:named:withInverse:] + 1434 7   Foundation                          0x00007fff878fe860
    NSKeyValueNotifyObserver + 390 8   Foundation<br>
    0x00007fff87900279 NSKeyValueDidChange + 456 9   Foundation<br>
    0x00007fff878bb7df -[NSObject(NSKeyValueObserverNotification)
    didChangeValueForKey:] + 130 10  CoreData<br>
    0x00007fff873898c1 -[NSManagedObject didChangeValueForKey:] + 113 11 
    CoreData                            0x00007fff873e566d
    -[NSManagedObject(_NSInternalMethods) _updateFromRefreshSnapshot:includingTransients:] + 685 12  CoreData                            0x00007fff873b0969 -[NSManagedObjectContext(_NestedContextSupport)
    _copyChildObject:toParentObject:fromChildContext:] + 121 13  CoreData                            0x00007fff873b0505 -[NSManagedObjectContext(_NestedContextSupport)
    _parentProcessSaveRequest:inContext:error:] + 629 14  CoreData                            0x00007fff873df72a __82-[NSManagedObjectContext(_NestedContextSupport)
    executeRequest:withContext:error:]_block_invoke_0 + 634 15 
    libdispatch.dylib                   0x00007fff8aad6a2d
    _dispatch_barrier_sync_f_slow_invoke + 77 16  libdispatch.dylib                   0x00007fff8aad10b6 _dispatch_client_callout + 8 17  libdispatch.dylib 
    0x00007fff8aad60c8 _dispatch_main_queue_callback_4CF + 275 18 
    CoreFoundation                      0x00007fff86e110fe __CFRunLoopRun
    + 1614 19  CoreFoundation                      0x00007fff86e106b2 CFRunLoopRunSpecific + 290 20  HIToolbox<br>
    0x00007fff89d950a4 RunCurrentEventLoopInMode + 209 21  HIToolbox<br>
    0x00007fff89d94e42 ReceiveNextEventCommon + 356 22  HIToolbox<br>
    0x00007fff89d94cd3 BlockUntilNextEventMatchingListInMode + 62 23 
    AppKit                              0x00007fff8ffcd613 _DPSNextEvent +
    685 24  AppKit                              0x00007fff8ffcced2
    -[NSApplication nextEventMatchingMask:untilDate:inMode:dequeue:] + 128 25  AppKit                              0x00007fff8ffc4283
    -[NSApplication run] + 517 26  AppKit                              0x00007fff8ff68cb6 NSApplicationMain + 869 27  callsfreecall<br>
    0x000000010e6ab472 main + 34 28  libdyld.dylib<br>
    0x00007fff858a47e1 start + 0 29  ???<br>
    0x0000000000000002 0x0 + 2</p>
  </blockquote>