gistfile1.m

    NSManagedObjectContext *theCreatingMOC = theChildMOC;

    [theCreatingMOC performBlockAndWait:^{

        // Insert some test data...
        NSManagedObject *thePerson = [NSEntityDescription insertNewObjectForEntityForName:@"Person" inManagedObjectContext:theCreatingMOC];
        [thePerson setValue:@"Steve Jobs" forKey:@"name"];
        
        NSManagedObject *theCompany = [NSEntityDescription insertNewObjectForEntityForName:@"Company" inManagedObjectContext:theCreatingMOC];
        [theCompany setValue:@"Apple" forKey:@"name"];

        [theCompany setValue:[NSSet setWithObject:thePerson] forKey:@"employees"];

        // And save it...
        NSError *theError = NULL;
        [theChildMOC save:&theError];
        NSLog(@"MOC Saved (%@)", theError);

        // Save our main MOC (if the inserts happen in a child MOC, saving the child MOC bubbles the changes up the main MOC, so we now have to save the main MOC)
        [theMainMOC performBlockAndWait:^{
            NSError *theError = NULL;
            [theMainMOC save:&theError];
            NSLog(@"MOC Saved (%@)", theError);
        }];

        // Store a object URL so we can do our magic in whatever MOC we want...
        theCompanyURL = theCompany.objectID.URIRepresentation;
        NSLog(@"%@", theCompanyURL);
        }];