Fetching relations with Core Data

Question

Hi,

I have two managed objects which have a bidirectional relationship. It is a 'segmentWithDetails' which contains a 'segment' object.

I use

NSEntityDescription *entity = [NSEntityDescription entityForName:@"SegmentWithDetails" 
                                          inManagedObjectContext:connectionDetailsService.connectionDetailsContext];
[fetchRequest setEntity:entity];

to get my segmentWith Details. This works ok.

BUT, when I try to retrieve the contained segment, I get nil.

I've tried to get it with

Segment *segment = [segmentWithDetails valueForKeyPath:@"segment"];

and with

Segment *segment = segmentWithDetails.segment;

But this does not work (=nil). I've also tried modifying the NSFetchedResultsController. I added the following:

[fetchRequest setRelationshipKeyPathsForPrefetching:[NSArray arrayWithObject:@"segment"]];
[fetchRequest setIncludesSubentities:YES];

But both of these do not seem to make any difference. From what I understand out of Apple fine documentation, the relationship should just work using faults.

What am I missing here? How do I get to the relationship object 'segment' from 'segmentWithDetails' ??

Answer 1

It should just work like you describe. Are you sure the "segment" object/relation actually exists and contains a real object? Check the data model that this relation isn't optional and check your code that you have actually stored something.

Answer 2

Problem solved. It was not how I read the data, but how I put it in CoreData. The posted code above is indeed correct. Thanx for the response Jaanus.