如何在CloudKit中创建记录作为孩子的记录列表？

Question

I want to have a record in the private database that represents a shopping list, and then I want to have child records of that shopping list that represent items on the shopping list. I'm wondering if that's possible, and if it is, should I implement it as just child records of the shopping list record or whether I should make "items" an attribute of the "shopping lists" record with NSArray type and then add the item CKRecords to that array.

It's not clear in the documentation whether a CKRecord can be a child of another CKRecord.

Answer 1

Have one record type to represent your shopping list and another record type to represent items on the shopping list.

In your shopping list record type, have a field that is an array of CKReferences, each of which points to an item record.

In your items record type have a field that is a CKReference that points back to the shopping list (eg called isOnShoppingList) and set its CKReferenceAction to DeleteSelf. This will ensure that the item gets deleted if the shopping list gets deleted.

(Edit: added reverse reference with CKReferenceAction = DeleteSelf.)

Answer 2

According to Apple , it's best to "organize your records around a central record type". This could be your shopping list record. Your shopping list item record would then be one of a possible many "additional record types to support the primary type".

To associate the two, Apple suggests we use something they call a "back reference" in the "Introducing CloudKit (Session 208) at WWDC 2014 . This would consist of having your shopping list item record maintain a reference back to the shopping list to which it is associated, rather than the other way around. This makes queries less intensive, because you can simply fetch list item records using the list's Id, rather than searching an array of references with each item for each list. Also, this design more closely aligns to the normal app interface design of displaying a list of shopping lists, then showing a list of items once a shopping list is selected.