Illegal attempt to establish a relationship 'xyz' between objects in different contexts

Question

I am using Apple\'s CoreDataBooks sample application as a basis for pulling data into a secondary managed object context in the background, and then merging tha

Answer 1

book *book = [mainContext ........]   //Get book from default context

NSManagedObjectID *objectId = [book objectID];

Book *tmpBook = [tmpContext objectWithID:objectId]; //Now book has the legal relationship