Core Data: Cross-model relationships
Core Data: Cross-model relationships
- Subject: Core Data: Cross-model relationships
- From: Ian Joyner <email@hidden>
- Date: Fri, 12 Oct 2007 16:40:59 +1000
I have some entities in my application that are global (like
preferences), and remain the same across application runs. These can
be referred to by entities that are specific to each stored document.
Thus I have a model which has a list of states that entities in each
separate document can be in. There is also a document model, which
describes the specific entities stored in each document.
Thus the entities in the document model refer to the state entities
in the preferences model. Now I can't use a relationship, because
Core Data does not support cross-store relationships. So I'm trying
to use a Fetched Property with a Fetch Request to define a weak cross-
store (and therefore cross-model) relationship.
Is this theoretically possible?
When I setup a fetched property for state in my document entity (in
Xcode modeller) it needs the destination set – however, the
destination popup only shows entities in the current model. What I
want (I think) is a predicate something like:
State.id == $FETCH_SOURCE.state_id
in order to relate the document entity to the globally defined state
entity in the other model.
If this isn't possible to setup in Xcode, can I do it programmatically?
Thanks
Ian
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