Re: Persistent store removal throwing invalidated NSManagedObject exceptions

[Drew McCormack]

Hi Drew,
When writing a custom to-many accessor in an NSManagedObject  
subclass, you need to invoke the correct KVO -will/didChange methods

These are:

-[NSManagedObject willChangeValueForKey:withSetMutation:usingObjects:]
-[NSManagedObject didChangeValueForKey:withSetMutation:usingObjects:]

So your method should change to:

-(void)removeCollectionsObject:(KnowledgeCollection *)anObject {
   NSSet *removedObjects = [[NSSet alloc] initWithObjects:&anObject  
count:1];
   [self willChangeValueForKey:@"collections"  
withSetMutation:NSKeyValueMinusSetMutation  
usingObjects:removedObjects];
   [[self primitiveValueForKey:@"collections"] removeObject:anObject];
   [self didChangeValueForKey:@"collections"  
withSetMutation:NSKeyValueMinusSetMutation  
usingObjects:removedObjects];
   [removedObjects release];
}

Hope this helps, there's a full example in the programming guide:

http://developer.apple.com/DOCUMENTATION/Cocoa/Conceptual/CoreData/Articles/cdAccessorMethods.html#/ 
/apple_ref/doc/uid/TP40002154-SW6

Jonathan

Thanks Jonathan. You're absolutely right.

However, when I made the appropriate changes, I have the same issue:  
with my new custom remove... accessor, I get the exception, and  
without the custom accessor, there is no exception. So something  
strange is still going on.

Here is the new accessor for good measure:

-(void)removeCollectionsObject:(KnowledgeCollection *)anObject {
    NSSet *removedObjects = [[NSSet alloc] initWithObjects:&anObject  
count:1];
    [self willChangeValueForKey:@"collections"  
withSetMutation:NSKeyValueMinusSetMutation usingObjects:removedObjects];
    [[self primitiveValueForKey:@"collections"] removeObject:anObject];
    [self didChangeValueForKey:@"collections"  
withSetMutation:NSKeyValueMinusSetMutation usingObjects:removedObjects];
    [removedObjects release];
}

Drew
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