I have the following model, as you can see in the image.

alt text http://img521.imageshack.us/img521/9741/schermata20100224a12251.png

My application requires refreshing every instance of B, so at each viewWillAppear, I need to delete all the B's in the model. Upon deleting a B, the cascade delete rule on the relationship to C will delete all C and then cascade to all D. A & E are constants.

I have the DeleteRule on each object as follows:

A: b - Cascade
B: c - Cascade, a - Nullify
C: b - Nullify, d - Cascade
D: c - Nullify, e - Nullify
E: d - Cascade

or

A -(cascade)->> B -(cascade)-> C -(cascade)->> D -(nullify)-> E
A <-(nullify)- B <-(nullify)- C <-(nullify)- D <-(nullify) E

I am having problem with cascading the delete on all B,C,D. My fetchRequest object returns every instance of B in A and then I call the -deleteObject: on each B from the managedObjectContext. But there is the EXC_BAD_ACCESS on the call to [managedObjectContext save:&error].

Can someone show me what I am doing wrong? Am I having problems with the DeleteRule on each entity or does the problem lay elsewhere? What are the best practices to handle the cascading deletes on three objects B,C,D?

Edited:

Here is the stack trace when the error is raised:

  #0    0x01d843ae in ___forwarding___
  #1    0x01d606c2 in __forwarding_prep_0___
  #2    0x01c618b6 in -[NSFetchedResultsController(PrivateMethods) _managedObjectContextDidChange:]
  #3    0x0003263a in _nsnote_callback
  #4    0x01d4f005 in _CFXNotificationPostNotification
  #5    0x0002fef0 in -[NSNotificationCenter postNotificationName:object:userInfo:]
  #6    0x01bc217d in -[NSManagedObjectContext(_NSInternalNotificationHandling) _postObjectsDidChangeNotificationWithUserInfo:]
  #7    0x01c21763 in -[NSManagedObjectContext(_NSInternalChangeProcessing) _createAndPostChangeNotification:withDeletions:withUpdates:withRefreshes:]
  #8    0x01ba65ea in -[NSManagedObjectContext(_NSInternalChangeProcessing) _processRecentChanges:]
  #9    0x01bdc728 in -[NSManagedObjectContext save:]

Here is the log in the console when I tried to set NSZombieEnabled & MallocStackLogging to YES:

  2010-02-24 15:41:39.803 Foo[2591:207] deleting object: FUM5
  2010-02-24 15:41:40.515 Foo[2591:207] *** -[viewController controllerWillChangeContent:]: message sent to deallocated instance 0x7e54510

Edit 2: SOURCE CODE ADDED

I have tried to recreate the situation by creating a new project with the exact schema in the image. You can download it from here. There is a README text as well. Hope that I have given enough information.

What are you doing in your NSFetchedResultsControllerDelegate methods? Based on the stack trace it looks like you are doing something funny in one of those. Ideally those delegates should only be updating the UITableView that they are attached to. If you are doing something either with the NSManagedObject instances or the NSManagedObjectContext in one of those methods it can cause a crash like this.

I would suggest putting a breakpoint on objc_exception_throw and that can give you more information about the exact point the issue is occurring.

Update

I have looked at the code and you are trying to delete a B while A has a required property for that B. This is causing a validation error. You can't delete an object that another object has as a required relationship.