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copying objects between two Core Data persistent stores?
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copying objects between two Core Data persistent stores?


  • Subject: copying objects between two Core Data persistent stores?
  • From: email@hidden
  • Date: Fri, 06 Jan 2012 16:48:28 -0500

I'd like to copy items between two different UIManagedDocument persistent stores. What is the proper way to do this?

Assuming I have a NSManagedObject subclass instance mo1 obtained from one UIManagedDocument, how do I properly copy the values from it to a newly inserted NSManagedObject subclass instance mo2 in the other UIManagedDocument?

Do I just run through all the properties I've defined for each attribute and do:
mo2.attribute = mo1.attribute
(which I could do by defining a method to do this)? I think this is ok, but I'm not 100% certain since these come from different NSManagedObjectContext instances so I want to be certain that won't cause a problem. Do all the properties need to be copy properties vs. strong/retain properties for this to work?

Or is there a better/simpler way to do this?

Also, I asked another Core Data question about four days ago, but never got a response. If you can answer this one too, that would be great.

=======================

If I create a child context of type NSMainQueueConcurrencyType such as:

   context = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];
   [context setParentContext:mainContext];

do I need to call [context performBlock:^{ // some code }];

or can I just use the context normally if I know the code is being executed on the main thread/queue?

Similarly, do I need to use performBlock on the UIManagedDocument's managedObjectContext property when I know the code is being executed on the main thread?

I think the answer to both questions is "no, you do not need to use performBlock", but I'd like to be certain.

=====================

Thanks,
Dave

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