Re: Core Data Lightweight Migration Woes
Re: Core Data Lightweight Migration Woes
- Subject: Re: Core Data Lightweight Migration Woes
- From: Quincey Morris <email@hidden>
- Date: Sun, 22 Aug 2010 11:55:21 -0700
On Aug 22, 2010, at 04:29, Jack Nutting wrote:
> On Sat, Aug 21, 2010 at 5:22 PM, Brad Gibbs <email@hidden> wrote:
>> Well, that's the way I started doing things, but, on pages 130-131 of the book More iPhone 3 Development (written by Dave Mark & Jeff LaMarche -- your co-authors for Learn Cocoa on the Mac) make a point of saying that the new version is the unnumbered version.
>>
>
> Well! Either I stand corrected, or I'll have to correct my compadres
> on that front...
Well, you're both wrong, really:
http://developer.apple.com/mac/library/documentation/Cocoa/Conceptual/CoreDataVersioning/Articles/vmVersioning.html
There's no actual version number for the compiled model, only a version string, and Core Data does nothing with it, other than to identify which model in a '.momd' package is the current model for the application. Also, there's no implied order amongst models. So, after duplicating a model in Xcode, you should be able to choose either the original or the copy as the current model.
>> I wish I could submit a simplified version to Apple, but, since I have no idea what's actually causing the problem and I can't seem to replicate it in the little test apps I've been making, I don't know how I'd do that. I do live about 45 minutes from Cupertino. Maybe it's time to pester Chris Hanson at the next NSCoder Night...
>>
>
> If you're just seeing this intermittently, then yeah, this is a
> mystery that may be hard to report a bug against.
The "intermittent" nature of the problem deserves some further attention, because there's absolutely nothing in the documentation (AFAICT) or in this thread so far that would explain the outcome being anything other than deterministic. It would be useful to know:
1. Given an already-created store and an already-built application that migrates the store, is the outcome always the same? (I mean, test by re-copying the files before each test run.)
2. If it is the same, what has to change to produce a different result? Re-creating the store? Re-building the application? Re-compiling the model? Changing the model?
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