Many-to-many relationships and Core Data

[pedrommcarrasco]

Are many-to-many relationships on Core Data still unsupported? 🤔

[mentrena]

Correct, CloudKit doesn't support them. CloudKit only supports many-to-one relationships by using a reference in each of the "many" records to the "one" record (see: https://developer.apple.com/documentation/cloudkit/ckrecord/reference)

[pedrommcarrasco]

Out of curiosity, does NSPersistentCloudKitContainer support them? - didn't see much information around 🤔

[mentrena]

That's a good question, the most I found is this:

All relationships must be optional. Due to operation size limitations, CloudKit may not save relationship changes atomically.
All relationships must have an inverse, in case the records synchronize out of order.
CloudKit doesn’t support the Deny deletion rule.

which doesn't specifically say it doesn't support many-to-many, although in my head inverse relationships don't make sense in the case of many-to-many relationships. But I haven't tried it myself –nor have I really used NSPersistentCloudKitContainer.

Actually, after reading the docs for CKRecord again I see properties can be arrays of references, so I think it should be possible to support many-to-many relationships. I'll have a try at adding support as time allows :)