CloudKit share Data between different iCloud accounts but not with everyone

Question

In my app I want to share data via iCloud with other iCloud users but not with the whole world but with selected other iCloud users.

I thought about a way this could work, but I am not sure if it will work and if I forgot or misunderstood some things.

Let s say User A wants to be able to share a string with other iCloud users but not with everyone. So User A wants to share „Hello World“ to User B but not to user C and not to User D.

So my app has a Public Data Base and a Record Type that is the same for everyone. In that Record Type there is a Field of type String that is also the same for everyone.

Now User A saves the record „Hello World“ to iCloud. And here comes the trick: I would add a unique identifier like UUID to the string so that something like „Hello World1230ABD6-3C61-1234-802E-D866F09AC012“ will be uploaded to iCloud.

Now User A needs to tell the User he wants to share the data with his UUID, so User A tells it to User B. Now the UUID of User A will be added as a Predicate to the CKSubscription of User B.

This will allow User B to fetch the string from User A, but User C or User D won t receive a CKNotification because they don t have the UUID of User A in their CKSubscription.

Is this going to work? Or is there another design pattern that allows sharing/syncing via iCloud with other iCloud accounts but not with everyone (public) ?

P.S. The data I want to share is not sensitive, so it does not need to be really secure. The data just isn t interesting for everyone (public) so it needs to be shared only to selected other iCloud accounts...

I am thankful for any thoughts or tips how to achieve this !

Thanks

Answer 1

CloudKit Sharing was introduced at WWDC 2016. This allows sharing of private database records between a known set of users, which is what it sounds like you're looking for. ...... There is a great overview in the "What's new in CloudKit" session: https://developer.apple.com/videos/play/wwdc2016/226/