All those “NSOrderedSet was added later and thus doesn’t have to play nice with other components” bugs drive me crazy…
I have two managed objects and an ordered 1:N relationship between them, which is backed by an instance (or more precise a subclass) of NSOrderedSet. I want to manage this relationship using a NSArrayController in order to profit from features it offers (selection management, binding of the content, bindings to views like NSTableView).
Since NSOrderedSet is not a subclass of NSSet, the contentSet binding of NSArrayController doesn't work with that relationship. I found following thread and tried to implement the suggestions mentioned there.
The first suggestion is to use the contentArray binding and a value transformer for transforming the ordered set to an array on the fly. The problem with this solution is the reassigning of the content each time a change is made, which is not what I want.
The second suggestion provided in the mentioned thread is to use the contentArray binding and apply the @array operator to the model key path. I've tried that, but the underlying relationship was not touched at all when adding/removing objects through the NSArrayController.
Another option I found is using sort descriptors with the contentSet binding. This would require making the relation unordered in order to make the contentSet binding work and introducing a new attribute used especially for managing the order. This would furthermore require a custom ordering mechanism to implement and it would mess up the model. Honestly said, I would like to avoid this solution.
My question is pretty clear: Is there any way to manage an ordered Core Data relationship using NSArrayController? If so, which is the best way causing as little pain as possible?