nsmanagedobjectcontext

As pointed out in another question on SO (and the Apple docs ), NSManagedObject instances do not hold a strong reference to the NSManagedObjectContext from which they originated. On first blush, this seems like a strange decision, since NSManagedObject instances are nearly useless without their context , since it leads to confusing bugs such as faults not firing when they should . Can anyone provide some background on why this is the case? Would it be dangerous to implement an NSManagedObject subclass that automatically holds a strong reference to its NSManagedObjectContext ? Edit: thanks to

I'm creating an NSManagedObjectContext in a private queue to handle data updates I take from files and/or services: NSManagedObjectContext *privateContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType]; AppDelegate *appDelegate = [[UIApplication sharedApplication] delegate]; privateContext.persistentStoreCoordinator = appDelegate.persistentStoreCoordinator; Since I'm using a private queue, I don't fully understand the difference between performBlock: and performBlockAndWait: methods... To perform my data updates I'm currently doing this:

My Cocoa/Application has a Managed Object Context on the main thread. When I need to update my data my program will: Start a new thread Receive new data from a server Create a new Managed Object Context Send a notification to the main thread in order to merge the two context This is the function that receive the notification on the main thread - (void)loadManagedObjectFromNotification:(NSNotification *)saveNotification { if ([NSThread isMainThread]) { [self.managedObjectContext mergeChangesFromContextDidSaveNotification:saveNotification]; } else { [self performSelectorOnMainThread:@selector

Is it possible to model relationships between entities that are defined in separate NSManagedObjectModels if the entities are always used within an NSManagedObjectModel that is created by merging the relevant models? For example, say model 1 defines an entity Foo with relationship (one-to-one) toBar and that model 2 defines an entity Bar with a relationship (one-to-one) toFoo . I will build a CoreData stack using -[NSManagedObjectModel mergedModelFromModels] , merging model 1 and model 2. Is there any way to define these relationships either in the data modeler or programatically so that they

In iOS 5, NSManagedObjectContext has a couple of new methods, performBlock: and performBlockAndWait: . What are these methods actually used for? What do they replace in older versions? What kind of blocks are supposed to be passed to them? How do I decide which to use? If anyone has some examples of their use it would be great. The methods performBlock: and performBlockAndWait: are used to send messages to your NSManagedObjectContext instance if the MOC was initialized using NSPrivateQueueConcurrencyType or NSMainQueueConcurrencyType . If you do anything with one of these context types, such

I have a problem that is almost identical to the problem described by this person here, but it hasn't get answered: http://www.cocoabuilder.com/archive/cocoa/312683-core-data-nested-managed-object-contexts-and-frequent-deadlocks.html#312683 Here is the problem: I have a parent MOC setup with NSPrivateQueueConcurrencyType and a persistent store coordinator set, it has a child MOC setup with NSMainQueueConcurrencyType. The idea being most of the long hard work and saves can be done on the private MOC freeing the main thread from blocking the UI. Unfortunately I seem to be running into a couple