CODEWITHSUNDEEP
objective-ccocoacore-datansmanagedobjectnsmanagedobjectcontext
JPC
JPC

Reputation: 8286

NSManagedObjectContext with different processes

I have two processes that are talking to the same persistent store. I save the context on one process, and I post a distributed notification. The other process sees the distributed notification, and fetches its data again, but still receives the old data. Is there some kind of "flushing" I need to do to get the other process to get the correct data from the store?

EDIT: So, it turns out that I was flushing the data correctly. NSManagedObjects have a "refreshObject:mergeChanges" method that you use to do this. The issue appears to be timing related. Let's say I have two processes, A and B. Process A is the main process and does a save to the database. Then Process B does a save to the database and sends a notification to Process A that it has done so, and Process A fetches the new data. I've found that if Process A's save and Process B's save are too close together, the old data is fetched by Process A even if I refresh. If I force there to be some time between the two saves, then it works out correctly.

Obviously this seems like some kind of race condition, where perhaps the notification is getting sent before the data is actually getting saved to the database, however, the notification gets sent in the didSave method of the managed object, at which point the context has already saved.

Upvotes: 0

Views: 481

Answers (1)

vicsonic
vicsonic

Reputation: 83

You should check the merge policy concept, to manage, get and communicate the correct values of a persistent store coordinator between different contexts.

Here -> http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/CoreData/Articles/cdChangeManagement.html#//apple_ref/doc/uid/TP30001201-CJBDBHCB

That should resolve the problem.

Hope this can help.

Upvotes: 1

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