A managed object context needs to be used and created from the same thread.
Create and use childContext in a single dispatchAsync block.
-Heath
On Aug 4, 2011 5:32 PM, "Jeff Kelley" <slauncha...@gmail.com> wrote:
> I’m having some issues with concurrency with Core Data. I create an object
> that has a to-many relationship with another object (which in turn has a
> to-one reciprocal relationship with the first object), then dispatch_async
> onto a private queue. In that queue, I use a separate managed object
> context, which I’ve created earlier and only use within that queue. Here’s
a
> snippet:
>
> ParentObject *parent = [NSEntityDescription
> insertNewObjectForEntityName:@"ParentObject"]
> inContext:[self moc]];
>
> NSManagedObjectID *objectID = [parent objectID];
>
> dispatch_async(dedicatedQueue, ^{
> // Note: childContext is an NSManagedObjectContext that has been created
> earlier and is only used within this queue.
> ParentObject *parent = [childContext objectWithID:userID];
>
> for (NSDictionary *jsonDict in allChildDicts) {
> ChildObject *child = [NSEntityDescription
> insertNewObjectForEntityName:@"ChildObject"]
> inContext:childContext];
> [parent addChildObject:child];
> }
> });
>
>
> If I try to save the context within the dedicated queue, I get validation
> errors on the child objects with the text “Dangling reference to an
invalid
> object.”
>
> It appears to work correctly if I create the parent object within the
> dedicated child queue. So, what is the proper way to create these objects
on
> the main queue and then update them in the background? Thanks in advance.
>
> Jeff Kelley
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