Placing items from a Core Data entity into an NSOutlineView programmatically?

Question

Sorry if this seems like a silly question - I am an amateur when it comes to Objective-C and Cocoa and even less knowledgable when it comes to Core Data usage.

So here's the situation: I have an NSOutlineView that I've already populated with a few items manually with an NSTreeController. What I need to do now is take the items in one of my Core Data entities and append them to the NSOutlineView's current contents.

Obviously this is beyond the abilities of bindings, so it will need to be done programmatically. What should I do? I assume that I need to do a fetch and then iterate through the returned items, adding each to the outline view. Is this correct? If so, would anybody be able to show an example of how this is done?

Thanks!

Answer 1

Create an NSFetchRequest with an NSPredicate that gets only those whose "parent" is nil (the root/top-level objects). Sort them by some attribute that makes sense (as the fetch results will be an unordered collection - an NSSet). Then implement the NSOutlineViewDataSource to mix/mingle the information as you see fit as it's provided to the outline.

Caution: It's best to cache your results, observing the context for changes and refreshing the cache on each change.