title: Core Data example, Invalid update: invalid number of rows in section 0
body: <p>I am novice at iOS and XCode, and am working through a Core Data tutorial and am really stumped. I continually get the error in the error logs of the following:</p>
  
  <pre><code>Exception Type:  EXC_CRASH (SIGABRT)
  Exception Codes: 0x0000000000000000, 0x0000000000000000
  Crashed Thread:  0  Dispatch queue: com.apple.main-thread
  
  Application Specific Information:
  iPhone Simulator 235, iPhone OS 4.2 (iPad/8C134)
  *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Invalid update: invalid number of rows in section 0.  The number of rows contained in an existing section after the update (0) must be equal to the number of rows contained in that section before the update (0), plus or minus the number of rows inserted or deleted from that section (1 inserted, 0 deleted).'
  *** Call stack at first throw:
  (
          0   CoreFoundation                      0x010a6be9 __exceptionPreprocess + 185
          1   libobjc.A.dylib                     0x00e9b5c2 objc_exception_throw + 47
          2   CoreFoundation                      0x0105f628 +[NSException raise:format:arguments:] + 136
          3   Foundation                          0x000b447b -[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:] + 116
          4   UIKit                               0x00336a0f -[UITableView(_UITableViewPrivate) _endCellAnimationsWithContext:] + 8424
          5   UIKit                               0x00325f81 -[UITableView insertRowsAtIndexPaths:withRowAnimation:] + 56
          6   SimpleRes                           0x00002496 -[RootViewController addReservation] + 465
          7   UIKit                               0x002b9a6e -[UIApplication sendAction:to:from:forEvent:] + 119
          8   UIKit                               0x004c7167 -[UIBarButtonItem(UIInternal) _sendAction:withEvent:] + 156
          9   UIKit                               0x002b9a6e -[UIApplication sendAction:to:from:forEvent:] + 119
          10  UIKit                               0x003481b5 -[UIControl sendAction:to:forEvent:] + 67
          11  UIKit                               0x0034a647 -[UIControl(Internal) _sendActionsForEvents:withEvent:] + 527
          12  UIKit                               0x003491f4 -[UIControl touchesEnded:withEvent:] + 458
          13  UIKit                               0x002de0d1 -[UIWindow _sendTouchesForEvent:] + 567
          14  UIKit                               0x002bf37a -[UIApplication sendEvent:] + 447
          15  UIKit                               0x002c4732 _UIApplicationHandleEvent + 7576
          16  GraphicsServices                    0x018bda36 PurpleEventCallback + 1550
          17  CoreFoundation                      0x01088064 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 52
          18  CoreFoundation                      0x00fe86f7 __CFRunLoopDoSource1 + 215
          19  CoreFoundation                      0x00fe5983 __CFRunLoopRun + 979
          20  CoreFoundation                      0x00fe5240 CFRunLoopRunSpecific + 208
          21  CoreFoundation                      0x00fe5161 CFRunLoopRunInMode + 97
          22  GraphicsServices                    0x018bc268 GSEventRunModal + 217
          23  GraphicsServices                    0x018bc32d GSEventRun + 115
          24  UIKit                               0x002c842e UIApplicationMain + 1160
          25  SimpleRes                           0x00001ab0 main + 102
          26  SimpleRes                           0x00001a41 start + 53
  )
  </code></pre>
  
  <p>Here is my addReservation code:</p>
  
  <pre><code>-(void)addReservation{
  
      // Create and configure a new instance of the Event entity.
      Reservations *reservation = (Reservations *)[NSEntityDescription insertNewObjectForEntityForName:@"Reservations" inManagedObjectContext:managedObjectContext];
  
      [reservation setEnd_Time: [[NSDate alloc]init]];
      [reservation setReservation_Date:[[NSDate alloc]init]];
      [reservation setStart_Time:[NSDate date]];
      [reservation setParty_Size: [NSNumber numberWithInt:4]];
      [reservation setPhone_Number: [NSNumber numberWithInt: 1234567890]];
      [reservation setName: @"Keith"];
      [reservation setNotes: @"He's really hot!"];
      [reservation setPerson_Responsible: @"Lisa"];
      [reservation setTables_Excluded: @"3,5,8"];
  
      NSError *error = nil;
      if (![managedObjectContext save:&amp;error]) {
          }
  
      [resArray insertObject:reservation atIndex:0];
      NSIndexPath *indexPath = [NSIndexPath indexPathForRow:0 inSection:0];
      [self.tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:indexPath]
                            withRowAnimation:UITableViewRowAnimationFade];
      [self.tableView scrollToRowAtIndexPath:[NSIndexPath indexPathForRow:0 inSection:0] atScrollPosition:UITableViewScrollPositionTop animated:YES];
  }
  </code></pre>
  
  <p>I believe that my resArray is not getting the data from the method that I input in programatically, but I am not sure, and I am not sure how to fix it.</p>
  
  <p>Any help is appreciated.</p>