Core Data Fetch Save relationship while inserting entity (simultaneously) - core-data

Question

First question here and I've tried a bunch of stuff and can't figure it out.
Core Data with 2 entities with to-many relationship both ways
A<<---->>B
A entity has name as an attribute, and a relationship Bs
First Controller lists all A entities and i have a second controller to add A entities and I want to have it save a default B in its relationship.
In the prepare for segue I have this code:
if ([[segue identifier] isEqualToString:#"addAEntitySegue"]) {
AddAEntityViewController *addAEntityViewController = [segue destinationViewController];
addAEntityViewController.delegate = self;
addAEntityViewController.managedObjectContext = self.managedObjectContext;
NSManagedObjectContext *addingContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];
self.addingManagedObjectContext = addingContext;
[addingManagedObjectContext setPersistentStoreCoordinator:[[fetchedResultsController managedObjectContext] persistentStoreCoordinator]];
addAEntityViewController.A = [NSEntityDescription insertNewObjectForEntityForName:#"A" inManagedObjectContext:addingContext];
UIBarButtonItem *saveButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemSave
target:addAEntityViewController
action:#selector(save:)];
addAEntityViewController.navigationItem.rightBarButtonItem = saveButton;
}
In addAEntityViewController i have this to save
-(IBAction)save:(id)sender
{
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:#"B" inManagedObjectContext:self.managedObjectContext];
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"name == %#",[defaults objectForKey:#"BDefault"]];
[fetchRequest setEntity:entity];
[fetchRequest setPredicate:predicate];
//Set the batch size to a suitable number
[fetchRequest setFetchBatchSize:20];
NSError *error;
self.A.name = textFieldVal;
[self.A addBObject:[[self.managedObjectContext executeFetchRequest:fetchRequest error:&error] objectAtIndex:0]];
NSLog(#"A = %#", self.A.Bs);
[self.delegate addAEntityViewController:self didFinishWithSave:YES];
}
In the addAEntityViewController everything saves correctly even the NSLog(#"A = %#", self.A.Bs); statement shows the B. But when the delegate saves in the First Controller (AEntityViewController) it only saves the A.name but not the relationship A.Bs, I can't figure out what's wrong.
Here's the delegate method:
-(void) addAEntityViewController:self didFinishWithSave:YES{
if (save) {
NSLog(#"saveworkouts");
NSError *error;
if (![addingManagedObjectContext save:&error]) {
// Update to handle the error appropriately.
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
exit(-1); // Fail
}
}
// release the adding managed object context
self.addingManagedObjectContext = nil;
}
Like I said it saves the A entity but not the relationship to B even though the relationship to B saved correctly in the addAEntityViewController (the second View). An NSLOg of A.Bs is null.

Answer 1

First I believe that this line:
addAEntityViewController = self.managedObjectContext;
should be:
addAEntityViewController.managedObjectContext = self.managedObjectContext;
but that would also be wrong.
it should be getting the addingContext you created afterwards:
addAEntityViewController.managedObjectContext = addingContext;
I'm a bit surprised that your app didn't crash, as you are mixing managed objects from 2 different contexts.