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I’m having an interesting problem. I have a basic CoreData app that uses an NSArrayController to manage some data in a table view. I wanted to add reordering of the data, so I subclassed NSArrayController, and implemented some table view data source methods, hooked them up… and it sort of works. When I drag reorder a row, I can see it appear where it should be for a second - then it’s deleted, instantly! I’ve tried this both with my code and a modified version of stuff on mmalcom’s site. At first I figured it was just a problem with my app, so I made a simple test project:

New CoreData app, add an entity called “Test”, with a string attribute for “name.” Insert an array controller, an add button, a table view. Hook them up. Insert my drag reorder stuff, reorder, row appears there for a split second, then the object is removed from the store. My code is below – any leads would be very much appreciated.

#import “DragReorderingArrayController.h”

NSString *MovedRowsType = @”MOVED_ROWS_TYPE”;

@implementation DragReorderingArrayController


Core Data uses [[NSSet and NSMutableSet, which do not support ordered indexing. There is no way to ensure data is stored or retrieved in order. The way around this is to add a property like -orderIndex to your entity and change that when rows are dragged. In other words, if #5 is moved to #3, everything from #3 and up is renumbered in the dragged order. Upon retrieval, you sort by the -orderIndex to maintain the dragged order.

Ah, well thanks for the tip.