Re: Preparing for MOM versioning in version 1
Re: Preparing for MOM versioning in version 1
- Subject: Re: Preparing for MOM versioning in version 1
- From: mmalc Crawford <email@hidden>
- Date: Mon, 26 Oct 2009 11:53:28 -0700
On Oct 26, 2009, at 9:00 am, Fritz Anderson wrote:
> I'm about to unleash a Core Data-based application, and I'm sure the schema will change in later versions. The Core Data Model Versioning and Data Migration Programming Guide seems to say that migrating a store from one version to another, at least in simple cases, is magical: The application embeds the historical MOMs, with one of them marked "current," and when a store built to an earlier model is opened, it is (in SIMPLE cases) migrated to the current model.
> Is this the case?
>
It's not clear what the question is. The implication appears to be that the documentation is simply presenting a fiction of functionality that's not actually present.
It's not magical.
Per the Guide (<http://developer.apple.com/mac/library/documentation/Cocoa/Conceptual/CoreDataVersioning/Articles/vmLightweight.html#//apple_ref/doc/uid/TP40008426>):
"To request automatic lightweight migration, you set appropriate flags in the options dictionary you pass inaddPersistentStoreWithType:configuration:URL:options:error:. You need to set values corresponding to both the NSMigratePersistentStoresAutomaticallyOption and the NSInferMappingModelAutomaticallyOption keys to YES..."
The (iPhone) PhotoLocations example (<http://developer.apple.com/iphone/library/samplecode/PhotoLocations/>) illustrates the feature.
mmalc
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