title: [CFNumber release]: message sent to deallocated instance
body: <p>The code below returns the following error when I log/request values from the History Core Data object:</p>
  
  <pre><code>-[CFNumber release]: message sent to deallocated instance 0x17ea2a90
  </code></pre>
  
  <p>I originally thought there was an issue elsewhere and have spent countless hours attempting to debug this to no luck. After further testing, I have pinpointed the crash to requesting certain values from the History Core Data object. Can anyone see any issues to why the object values are being deallocated? </p>
  
  <pre><code>    [[DocumentHandler sharedDocumentHandler] performWithDocument:^(UIManagedDocument *document) {
  
      if(!self.document) {
          self.document = document;
      }
  
      __block NSString *identifier = [[NSUserDefaults standardUserDefaults] objectForKey:kUserDefaultsUserIdentifier];
  
      [self.document.managedObjectContext performBlock:^{
  
          // Create history object
          History *history      = [NSEntityDescription insertNewObjectForEntityForName:@"History"
                                                                inManagedObjectContext:self.document.managedObjectContext];
          history.identifier    = identifier;
          history.followers     = [NSNumber numberWithInteger:53];
          history.following     = [NSNumber numberWithInteger:53];
          history.newFollowers  = [NSNumber numberWithInteger:53];
          history.unfollowers   = [NSNumber numberWithInteger:53];
          history.fans          = [NSNumber numberWithInteger:53];
          history.mutualFriends = [NSNumber numberWithInteger:53];
          history.nonFollowers  = [NSNumber numberWithInteger:53];
  
          [self.document saveToURL:self.document.fileURL forSaveOperation:UIDocumentSaveForOverwriting completionHandler:^(BOOL success) {
  
              // Fetch previous records
              NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"History"];
              request.predicate
              = [NSPredicate predicateWithFormat:@"identifier == %@", identifier];
  
              NSError *error = nil;
  
              NSArray *records = [self.document.managedObjectContext executeFetchRequest:request error:&amp;error];
  
              [records enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
                  NSLog(@"%@", [(History *)obj newFollowers]); // Crash takes place here
              }];
  
          }];
  
      }];
  
  }];
  </code></pre>
  
  <p>More logs with an exception breakpoint enabled:</p>
  
  <pre><code>    (lldb) bt
  * thread #1: tid = 0x28b70, 0x3b5787fa libobjc.A.dylib`objc_release + 10, queue = 'com.apple.main-thread, stop reason = EXC_BAD_ACCESS (code=1, address=0x10)
      frame #0: 0x3b5787fa libobjc.A.dylib`objc_release + 10
      frame #1: 0x3b578022 libobjc.A.dylib`(anonymous namespace)::AutoreleasePoolPage::pop(void*) + 358
      frame #2: 0x311b4298 CoreFoundation`_CFAutoreleasePoolPop + 16
      frame #3: 0x3127533e CoreFoundation`__NSArrayEnumerate + 614
      frame #4: 0x31216012 CoreFoundation`-[NSArray enumerateObjectsWithOptions:usingBlock:] + 62
      frame #5: 0x000eae26 Twitter Followers`__71-[MainViewController updateCurrentRecordAndTableHeaderForUpdateAction:]_block_invoke_2(.block_descriptor=0x15e58080, success='\x01') + 678 at MainViewController.m:671
      frame #6: 0x3ba65bea libdispatch.dylib`_dispatch_barrier_sync_f_slow_invoke + 66
      frame #7: 0x3ba600ee libdispatch.dylib`_dispatch_client_callout + 22
      frame #8: 0x3ba629a8 libdispatch.dylib`_dispatch_main_queue_callback_4CF + 268
      frame #9: 0x3124b5b8 CoreFoundation`__CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 8
      frame #10: 0x31249e84 CoreFoundation`__CFRunLoopRun + 1308
      frame #11: 0x311b4540 CoreFoundation`CFRunLoopRunSpecific + 524
      frame #12: 0x311b4322 CoreFoundation`CFRunLoopRunInMode + 106
      frame #13: 0x35eeb2ea GraphicsServices`GSEventRunModal + 138
      frame #14: 0x33a6b1e4 UIKit`UIApplicationMain + 1136
  </code></pre>