Synchronizing based on document id (shared via link) instead of user id (array of collaborators)

MongoDB Atlas App Services & Realm
,
1

I am trying to share documents with a link website.com/items/:id.

class Item: Object, ObjectKeyIdentifiable {
    @Persisted(primaryKey: true) var _id: ObjectId
    @Persisted var userId: String
    @Persisted var name: String
}

If a user opens the link (I am using universal links so they are opened in the app), I want to start synchronizing based on the document id so that the item can be edited on any device.

class SharedWithMe: Object, ObjectKeyIdentifiable {
    @Persisted(primaryKey: true) var _id: ObjectId
    @Persisted var userId: String
    @Persisted var item: Item
}

To accomplish this, I introduce a SharedWithMe document that has a user id.

extension User {
    func createFlexibleConfiguration() -> Realm.Configuration {
        let config = self.flexibleSyncConfiguration(initialSubscriptions: { subs in
            if subs.first(named: "user_items")  == nil {
                subs.append(QuerySubscription<Item>(name: "user_items") {
                    $0.userId == self.id
                })
            }
            
            if subs.first(named: "shared_with_me")  == nil {
                subs.append(QuerySubscription<SharedWithMe>(name: "shared_with_me") {
                    $0.userId == self.id
                })
                
//                subs.append(QuerySubscription<Item>(name: "shared_items") {
//                    $0.id == SharedWithMe.item.id
//                })
            }
        })
        return config
    }
}

I am not sure how to write a more advanced subscription query for Item that searches the SharedWithMe collection.

I could create a subscription when opening a link, but then other devices wouldn’t be aware of that subscription.

let parsedId = "123"
let sharedWithMe = SharedWithMe()
sharedWithMe.userId = user.id
sharedWithMe.item.id = parsedId // Cannot assign to property: 'id' is a get-only property
subs.append(QuerySubscription<Item>(name: parsedId) {
    $0.id.stringValue = parsedId
})