Re: Core Data: Cross-model relationships
Re: Core Data: Cross-model relationships
- Subject: Re: Core Data: Cross-model relationships
- From: Ian Joyner <email@hidden>
- Date: Mon, 15 Oct 2007 16:39:46 +1000
Since no one has had a go at this one, I'll assume that the answer is
no, you cannot set up cross-model relationships (or fetched
properties) in Xcode modeller.
I think the way to do it is in code setting up a new
NSFetchedPropertyDescription with an appropriate NSFetchRequest.
Should know more tomorrow about how this works.
Thanks
Ian
On 12/10/2007, at 4:40 PM, Ian Joyner wrote:
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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