shufflingb / swiftui-foreach-drag-core-data Goto Github PK

Issue

ContentView.rearrangeChildItems has to clone the Core Data ordered set from an NSOrderedSet to a NSMutableOrderedSet before it can (using the moveObjects to) be rearranged

There a performance impact (seems acceptable with up to ~50 items) which should not be necessary, as:

1. According to the official documentation for the data modeller as it states: "Arrangement: Select the Ordered checkbox to specify that the relationship has an inherent ordering, and to generate an ordered mutable set.".
2. The App's Core Data model uses that option for its children and parent relationships.

And yet XCode's (11.6 and 12 Beta 3) Editor> Create NSManagedObjectSubclass Subclass... generates accessors for the sets in Item+CoreDataProperties, it creates items that return immutable NSOrderedSet.

Misc

In the hope that Core Data's mapping was simple screwy, I tried:

1. casting to NSMutableOrderedSet in ContentView.rearrangeChildItems.
2. Changing the returned type in Item+CoreDataProperties for the lists ``NSMutableOrderedSet`

Neither worked, and from memory, built, allowed rearrangement, but then silently i.e. no exceptions or warnings, failed to persist the data.

Issue

With a many item paged lists, a successful drag operation always results in the screen of items displayed snapping back to the first page of data regardless of on what screen the moved item was actually dropped.

Expected behaviour would be that the moved item would remain visible post move.

Replicate

XCode 11.6
iOS 13.6

1. Create a couple of screenfuls of data by pressing the add item button. i.e. to view the end of it requires scrolling.
2. Scroll to the end of the list and note its UUID
3. Move the end item up one spot in the list and observe that the:
   a. Screen is showing the the top of the list
   b. Moved item's UUID is no longer visible.