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    <p>You cannot roll back only a partial change set of an <code>NSManagedObjectContext</code>. The best way to do what you're talking about is to make a new <code>NSManagedObjectContext</code> that is a child of a parent context. When you save it, the changes get pushed to the parent (you have to make sure that you save your parent contexts to actually persist to disk). Additionally, if you isolate change sets in this manner, you don't even have to call <code>rollback</code> on the child contexts, you can just throw them away.</p> <p>Note that to use the parent/child relationships of the <code>NSManagedObjectContext</code> you must the <code>initWithConcurrencyType:</code> method to initialize all your contexts, and you must specify either <code>NSPrivateQueueConcurrencyType</code> or <code>NSMainQueueConcurrencyType</code>. It is important to note that this has implications on how you access the context. If you are not on the main queue using a context with a concurrency type of <code>NSMainQueueConcurrencyType</code>, you will have to put all method calls that interact with the context inside a block and pass it to the contexts <code>performBlock:</code> or <code>performBlockAndWait:</code> method.</p> <p>The documentation is rather thin on this topic. The only reference I can find outside of WWDC videos is in <a href="http://developer.apple.com/library/ios/releasenotes/DataManagement/RN-CoreData/index.html" rel="nofollow">this iOS 5 release notes document</a>.</p>
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    1. USCharles A.
    1. USCharles A.
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    1. COThis solution is exactly what I am looking for. I have still a problem. Say if there is a core data object obtained from the first controller, and it is in the parent MOC. Later the second controller is pushed and it wants to edit the object in the child MOC. How am I supposed to move the object to the second MOC then? Thank you.
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    2. COYou would have to move the new object via the parent MOC. If you've got a child MOC and you save changes, they get pushed to the parent. If you then make another child MOC of that same parent, it will have everything that got pushed to the parent. If you have two child MOCs that exist at the same time, you might have to re-fetch objects in the second child after the first child saves. You would do this by executing your fetch request again, potentially with its `shouldRefreshRefetchedObjects` property set to `YES`.
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    3. COWhat I meant is like this: Say an objectA is obtained in Controller A. And its MOC is the first one, i.e. objectA.MOC is MOC1. Then I want to do some changes of this object in controller B, but within MOC2. I want to do some like objectA.MOC = MOC2 (this can not be done as .MOC is readonly). So is there any way to assign the object to MOC2? because I do not want to get the object again under MOC from database tables, as the selection might return many objects which share the same selection condition.
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