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Apple introduced ordered to-many-relationships in Core Data in Lion. I created an entity named TreeNode with an 1:1-object-relation, a 1:1-parent-relation and an ordered to-many-relationship children.

Then I have an NSTreeController with the children key path set to TreeNode.children. Running the application only shows first level elements. So children is not working. Since children is an ordered to-many-relationship, the corresponding class has an NSOrderedSet children. I added a custom method

- (NSArray *) childrenArray {
  return [children array];
}

to TreeNode which works. I could not find any documentation concerning that topic. Is it really the way to go when binding NSTreeController to an ordered to-many-relationship? Thanks in advance.

Marius Heidenstecker
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    I haven't used ordered relationships like this yet but tree controllers have always been notoriously fussy. I would suggest getting it to work without the ordering first and then add the ordering. – TechZen Aug 12 '11 at 15:23
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    I'm having the same issue as well. Is there any working example of NSTreeController working together with Ordered CoreData relationships? – Tony Dec 20 '11 at 01:47
  • Simply adding the childrenArray method solved the problem for me! – Elmer Cat Jun 23 '13 at 18:12

1 Answers1

4

It seems that Apple gave us ordered sets for Core Data but forgot to upgrade its binding controllers. One year later after your question, the problem is still there.

Have a look at:

https://github.com/robertjpayne/DDOutlineView

Moral of the story. Be careful when using ordered relationships, try to do your own implementation until Apple fully implements that feature

SystematicFrank
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