Matching CoreData save notifications for callbacks

I'd like to pick someone's brain on this. I have a dedicated save NSManagedObjectContext and GCD queue from which I operate on it. And whenever new data comes into my app I save it on that context and merge the changes into the main context. My problem arises in telling the main thread what just happened. Right after I call save my current context is now up-to-date, but if I fire a method in the main context it's context isn't. If I wait for the NSManagedObjectContextDidSave notification, and I save three times, I now have three queued delegate calls but no way to match them to the notifications coming in. Does anyone know of a good way to get around this?

EDIT

What I ended up doing was creating a new context for each save operation and attaching a block to be called when the save notification arrived. It looks like this,开发者_C百科 http://pastie.org/2068084

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From your answer to my comment above, I see that you pass along the managedObjectContext in the notification. I'm not that confident about asynchronous stuff yet, but I do think that you're violating some concurrency rule, if I correctly interpret this quote from the NSManagedObjectContext Class Reference:

Concurrency Core Data uses thread (or serialized queue) confinement to protect managed objects and managed object contexts (see “Concurrency with Core Data”). A consequence of this is that a context assumes the default owner is the thread or queue that allocated it—this is determined by the thread that calls its init method. You should not, therefore, initialize a context on one thread then pass it to a different thread. Instead, you should pass a reference to a persistent store coordinator and have the receiving thread/queue create a new context derived from that.

I'd say, try passing along the persistent store coordinator in the notification and recreate the managed object context in the block.

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I'm not sure what you mean by, " ...if I fire a method in the main context it's context isn't. If I wait for the NSManagedObjectContextDidSave..." That implies that you are not waiting until the contexts have been merged. If so, that is why you can't access the data, it's just not in the front context.

Do you call mergeChangesFromContextDidSaveNotification: from the front context after it receives the notification?