CODEWITHSUNDEEP
xcodecore-data
RonLugge
RonLugge

Reputation: 5174

Why is my core data object loosing it's relationship?

I have the following code in viewDidLoad:

NSManagedObjectContext *moc=[[NSManagedObjectContext alloc]
                              initWithConcurrencyType:NSMainQueueConcurrencyType];
[moc setParentContext:[AppCoreDataHandler sharedManagedObjectContext]];
self.restroom=[NSEntityDescription insertNewObjectForEntityForName:@"Restroom"
                                            inManagedObjectContext:moc];
self.restroom.coordinate=[((AppDelegate *)[[UIApplication sharedApplication] delegate]) locationManager].location.coordinate;
self.review=[NSEntityDescription insertNewObjectForEntityForName:@"Review"
                                          inManagedObjectContext:moc];
[self.restroom addReviewsObject:self.review];

Testing using the debug console shows that self.restroom.reviews is equal to an NSSet containing a review. By the time I reach 'viewWillAppear', self.restroom.reviews is nil. I'm not setting reviews to nil ANYWHERE in my code. Self.review remains completely valid the entire time. It simply doesn't make sense!

I'm at my wits end trying to figure this out. It can't be any multithreaded code, I'm not assigning anything else to the property/relationship, the object isn't weakly retained and releasing itself, it just... vanishes. Why?

Edit: Even more fun, I used key value observing to check on WHEN the value is changed.

From what I can read of the stack trace, it's being changed INSIDE the viewDidLoad function. But when I step-through the code, the key value notifications are clearly sent AFTER the function ends.

Upvotes: 0

Views: 41

Answers (1)

RonLugge
RonLugge

Reputation: 5174

By pure dumb luck (read: hrm, I wonder if... nope. Ok then. I wonder if... and repeat for about two bazillions iterations), I figured it out.

The child MOC I created for these objects gets deallocated not after the last reference to it (which is what I'd expect ARC to do), but rather at the end of the function. And when it dies, it didn't deallocate the objects it was assigned to, but it did strip them of their relationships. (I'm going to guess that while it LOOKS like an NSSet is providing those, it was actually something in the guts of the MOC).

Upvotes: 1

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