CODEWITHSUNDEEP
objective-ccore-data
JoeS
JoeS

Reputation: 231

My Core Data one-to-many objects seem to be losing their class

I have a project which uses Core Data. There is an entity called CDGroup which has a one to many relationship with an entity called CDChapter, the relationship is called chapters. They both have corresponding classes (which are subclasses of NSManagedObject.)

When I retrieve a CDGroup object its class is CDGroup which is correct, the issue however is that if I then attempt to access the chapters set of that group like this:

 NSLog(@"%@",[group.chapters objectAtIndex:0].name);

I get an error because the chapter that is retrieved is of type NSManagedObject not CDChapter. I've tried casting the chapter to the correct class but I still get the same issue.

How do I make this work?

Thanks,

Joe

Upvotes: 0

Views: 80

Answers (2)

Raphael Ayres
Raphael Ayres

Reputation: 894

chapters refers to an NSSet of objects that belong to the relationship. Try using:

((CDChapter*)[[group.chapters allObjects] objectAtIndex:0]).name;

Upvotes: 0

jrturton
jrturton

Reputation: 119242

You can't use dot notation with cast objects. Either split the call out into two lines:

CDChapter *chapter = [[group.chapters allObjects] objectAtIndex:0];
NSLog(@"%@",chapter.name);

Or use the accessor method rather than dot notation:

NSLog(@"%@",[(CDChapter*)[[group.chapters allObjects] objectAtIndex:0] name]);

Upvotes: 2

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