NSArrayController that is sorted and unique (no duplicates) for use in a pop-up in a core-data app

I have core data app with an entity OBSERVATION that has as one of its attributes DEALNAME. I want to reference through Interface Builder or by making custom modifications to an NSArrayController a list of unique sorted dealnames so that I can use them in a pop-up.

I have attempted to use @distinctUnionOfSets (and @dist开发者_开发技巧inctUnionOfArrays) but am unable to locate the proper key sequence.

I can sort the ArrayController by providing a sort descriptor, but do not know how to eliminate duplicates.

Are the @distinct... keys the right methodology? It would seem to provide the easiest way to optimize the use of IB.

Is there a predicate form for removing duplicates?

Or do I need to use my custom controller to extract an NSSet of the specific dealnames, put them back in an array and sort it and reference the custom array from IB?

Any help would be appreciated. I am astounded that other have not tried to create a sorted-unique pop-up in tableviews.

You need to take a look at -[NSFetchRequest returnsDistinctResults]. That is the level you need to be handling the uniquing of data.

Although I do not have a definitive answer for you, I think there are two ways you can go about it.

1. The way you already started. You need to bind the contents array of the PopUp button, not just against the arrayController.arrangedObjects, but continue on the path and somehow filter only objects with distinct "DealName"s. This means - the arrayController presents ALL the entities (and may sort them for you) but the PopUp button will have its contents filter via some sophisticated binding to the array controller.

2. Make your filtering at the ArrayController level (as suggested in another answer here). Here it depends how you set up the array controller. If It is set up to use an "Entity" (vs. "Class") which means the array controller will fetch CoreData entities directly - you can modify its "Fetch" to only bring a subset of the "OBSERVATION" entities with distinct values of "DEALNAME". I don't know how to control WHICH entities are filtered out in this case. Otherwise, you can setup the arrayController to work with "Class" objects, and then you can fetch the entities yourself (in code) and populate the arrayController programmatically, with just the entities you like.

In the second option, the Popup button should be bound normally to the arrayController's arrangedObjects.