Core Data Relationships cause save error after delete

Check your xcdatamodel file for a Deny delete rule. Click on each relationship until you find it. You'll need to change this rule or adjust how you delete managed objects to anticipate the rule's application to the relationship.

I just had the problem of delete fail, and landed on this question. And I've figured out my problem and thought that I'd share that too and maybe someone will have the same problem as well.

The mistake I made is that the object (A) I am trying to delete have a relationship to another object (B) with NULL as delete rule. However, object B also have a relationship to A and it's non-optional. Therefore, when I delete A, B's relationship of A becomes null which is not allowed. When I change the delete rule to cascade and it worked.

I can't mark this solved, because I didn't really solve it, but I do have a working work-around. In the .m for each of my managedObjects I added a method that looks like:

-(void) deleteFromManangedObjectContext{ 
   self.outfit = nil; 
   self.article = nil; 
   [[self managedObjectContext] deleteObject:self]; 
} 

So you can see, first I manually nil out the relationships, and then I have the object delete itself. In other objects, instead of nil-ing, my delete method is called on some of the objects relationships, to get a cascade.

I'm still interested in the "right" answer. But this is the best solution I have, and it does allow for some fine-grained control over how my relationships are deleted.

Do you happen to implement some of the accessor to the relationship yourself? I once had a code like

-(NSSet*)articles
{
       re-calculates properties....
       return [self primitiveValueForKey:@"articles"];
}

in a subclass of NSManagedObject and had a save error. What happened was that, when this object is deleted from the ManagedObjectContext, the CoreData calls the accessor "articles" to deal with the delete propagation. This re-calculation of articles occurred during the delete propagation, which re-surrected the nullified "articles" in my case.