On 31 Jul 2011, at 16:58, Jim Thomason wrote: > Gang, > > I've encountered an odd bug/issue/feature(?) in Lion and want to know > if there's a workaround available. > > I have a multithreaded CoreData application. It does a lot of > calculations on the context, so it spawns off a separate thread and > creates a new ManagedObjectContext to do its work. AFAIK, I'm > following proper Best Practices for multi-threaded core data access. > This all works fine. > > The issue is, at the start of my thread, I call saveDocument: on the > main context, in the main thread via this: > > [self performSelectorOnMainThread:@selector(saveDocument:) > withObject:nil waitUntilDone:YES]; > > I didn't want to worry about jumping through the hoops of merging the > contexts, so I just ensure the main context is clean and saved. It > invokes saveDocument, then checks to see if the context still has > changes, and if it does it bombs out and refuses to continue, assuming > that the save failed for some reason. > > This works fine under Snow Leopard (and Leopard, and it used to work > under Tiger as well, though I no longer support that OS). But under > Lion, it fails since it doesn't actually wait until the save is > complete. It looks like pre-Lion, saveDocument: would directly invoke > the writeToURL:... method, whereas in Lion it's deferring it until the > next invocation of the run loop. > > So under Snow Leopard, I'd see this behavior: > > SECOND THREAD: perform saveDocument on Main, wait until done > MAIN THREAD: call saveDocument > MAIN THREAD: call writeToURL:... > SECOND THREAD: done waiting for main to complete, carry on. > > But now on Lion, I see this: > > SECOND THREAD: perform saveDocument on Main, wait until done > MAIN THREAD: call saveDocument > SECOND THREAD: done waiting for main to complete, carry on. Sees that > the main MOC still has changes, fails out. > MAIN THREAD: call writeToURL:... > > So Lion waits for saveDocument: to finish, but then writeToURL:... is > called later. I have a simple test case to verify: > > http://www.prototypesite.net/threadedsavetest.zip > > If you run it on Lion, writeToURL is called after the second thread is > done waiting. If you run it on Snow Leopard, it's done before. > > Is this a bug or a feature? If it's a feature and expected to behave > this way, then what's the proper way for me to get this behavior now, > in a way that's backwards compatible on Snow Leopard and Leopard?
-saveDocument: has never been expected to do its work immediately. Instead, you want to call: -saveDocumentWithDelegate:didSaveSelector:contextInfo: Then, when the delegate is called, spawn off your new MOC._______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
