I found some sample code that addresses this:
http://shanecrawford.org/2008/37/sorting-a-coredata-backed-nsarraycontrolle
r/
On Aug 7, 2009, at 2:50 PM, Brad Gibbs wrote:
> Hi,
>
> I have an NSTableView that displays a set of Activity objects, which
> are subclasses of NSManagedObject, all of which are managed by a
> custom NSArrayController. Each Activity has a sortIndex property,
> which is used to... wait for it... sort the activities.
>
> The array controller adds logic to update the sortIndex as objects
> are added, removed or re-ordered. It's this last part that's giving
> me grief. The table supports drag-and-drop. The idea is that when
> an Activity is dragged up or down in the list, the sortIndex for all
> of the activities get updated, so that the next time the list of
> activities is displayed, the activities maintain the order in which
> they were placed by the user.
>
> The array controller's sort descriptors binding is bound to an array
> with a single NSSortDescriptor, set to order the objects by
> sortIndex. I think this is causing some grief. Also, the code that
> assigns new sortIndexes for each object calls [arrayController
> arrangedObjects] to get the array controller's objects. From my
> reading of the documentation, this calls arrangeObjects on the
> underlying array, which I don't really want to do until all of the
> Activity objects' sortIndexes have been updated to reflect their new
> positions in the array.
>
> The objects that are dropped are assigned new sortIndexes based on
> their new indexes immediately after being dropped into the array.
> I'm not doing anything with the sortIndexes for the items in the
> array that haven't been moced until later. In the interim, I
> believe that calling [arrayController arrangedObjects] is trying to
> make the NSArrayController arrange its objects based on its sort
> descriptor (sortIndex), while one or more of the objects in the set
> share the same sortIndex. This is causing problems.
>
> I'm hoping someone can point me to some sample code that addresses
> this issue. I've looked at Demo Monkey and a couple of other
> samples I found on the web without being enlightened. Jonathan Dann
> has sample code using sortIndex and an NSTreeController, but
> updating the treeController doesn't involve rearranging its items
> first, so, it doesn't quite work.
>
> Possible solutions I can see:
>
> 1. manually assigning new sortIndexes to all objects from the point
> of insertion through the end of the array / set immediately upon
> insertion of the moved objects, or:
> 2. copying the entire array after insertion and then using the
> copied array to assign new indexes:
>
> for (Activity *anActivity in activitiesArrayCopy) {
> [anActivity setValue:[NSNumber numberWithInt:[activitiesArrayCopy
> indexOfObject:anActiviity]] forKey:@"sortIndex"]
> }
>
> But, I think there's a cleaner, more elegant solution out there that
> I'm not seeing.
>
> Any suggestions would be appreciated.
>
>
> Thanks.
>
> Brad
