Re: Multi-storage Core Data
Re: Multi-storage Core Data
- Subject: Re: Multi-storage Core Data
- From: Rob Napier <email@hidden>
- Date: Thu, 22 May 2008 12:05:29 -0400
On May 17, 2008, at 3:54 PM, Jim Correia wrote:
On May 17, 2008, at 3:00 PM, Keary Suska wrote:
on 5/17/08 10:27 AM, email@hidden purportedly said:
I'm trying to build a Core Data app for which some data is user-
provided and
some data is shipped with the program. Consider a travel itinerary
program
for instance where the user has a trip from airport A to airport
B. If the
program includes data about the airports themselves, that
shouldn't be
stored in the same storage as the user's flight numbers. One is
document
based and the other is shared across documents.
I understand the basic idea of using Fetched Properties and how to
create
them. What I'm not clear on is how to define a fetched property in
one store
against objects in another store, or how to tie multiple stores
together
into a context. Is there a good explanation or sample code for
this kind of
setup?
I don't believe there is any support for this, at least not
"automatically".
You would have to provide glue code for any interactions between
Managed
Object Contexts (MOCs), since each MOC is married to one storage.
This is not quite correct.
A MOC is associated with a persistent store coordinator. A PSC can
have multiple stores associated with it.
What you do not get for free is cross-store relationships.
Which is how I understood it, and I'm willing to write some glue here.
But do you have any pointers on how to get started with that? I
haven't been able to figure out with a multi-store PSC, how to direct
some objects to one store and others to another. Examples of using
fetched properties to create cross-store relationships are also seems
pretty thin in the main docs. Are there any good references on Core
Data beyond the fairly straight-forward Department app?
It looks like there have been many CD improvements in Leopard
(transformable attributes being the one that really jumps out to me).
It looks like it may be time for me to re-read all the docs and try
again with the new 10.5 features.
-Rob
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