CoreData + CloudKit -- Many-to-Many Relationship not Syncing

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Created 5d

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In an iOS App that uses CKShare I have a many-to-many relationship that does not consistently sync between the share's N participants. The relationship is between Group and Player as group.players and player.groups. As an example, given 3 group each with 4 players (aka 4:4:4), some devices show CoreData (it is NOT a UI issue) with 4:2:3 or 3:4:4.

(A deletion of CoreData from a device, forcing a full re-sync from CloudKit, seems to populate the group:player relationships consistently; but obviously that is impractical to resolving the issue).

How do I avoid these sync-from-CloudKit inconsistencies?

Note: AI agents generally suggest adding a CoreData 'join' entity - such as 'GroupPlayer'. Is that THE fix?

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Answer 1

DTS Engineer OP

Apple

5d

This sounds like a general synchronization issue, and so you can probably start with the technotes mentioned in this post to hopefully figure out the cause of the issue.

NSPersistentCloudKitContainer supports many-to-many relationships. Before seeing an evidence that proves it doesn't work (by going through the debugging process the technotes describe), I probably won't change the Core Data model.

Best,
——
Ziqiao Chen
 Worldwide Developer Relations.

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