Question

Consider the following code:

[context performBlock:^{
    // add a bunch of objects to context

    NSError *error;
    if(![context save:&error])
        NSLog(@"Couldn't save MOC because of error: %@", error.localizedDescription);
}];

This is inside a “Store Manager” class, which has getters for 2 MOCs: a standard .objectContextand a .backgroundObjectContext, which is initialized with the following:

backgroundObjectContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType];
backgroundObjectContext.parentContext = self.objectContext;

My problem: when I set context to self.objectContext, everything is fine and the data is saved to the .sqlite file. When I set it to self.backgroundObjectContext, no data is written to the sqlite file, but save: returns YES with no error. I tried logging that context’s registeredObjects and everything is there. How come the data doesn’t get written to the sqlite file?

I’ve been using the new MOC iOS 5 APIs for a while and this is the first time I’m encountering this issue, so I’m pretty clueless. Is that how you initialize a background MOC in iOS 5? Is there anything else I might be missing here?

Answer 1

When you save a childContext, changes are merged with the parentContext. To be written to a file, you need to save the context at the root.

So in this case:

• you save backgroundObjectContext to merge changes with objectContext

• you save objectContext to save to the PSC