Question

I have an entity called guestlist that has a 1 to many relationship to an entity called guest. Guestlist also has a relationship to the Invite entity.

When I create an Invite object with a guestlist that contains a guest object. It saves fine and displays within the app fine. Next I create another Invite with a different title, a new guest list object, with the same guest. This also saves fine and displays within the app fine.

The problem is that when I exit the app and come back in, only the most recent Invite retains the relationship of guestlist to guest(s). The timestamp value on the guest list is there but the relationship to the guest(s) objects are empty.

Here is the code I use to set the objects and save them into the store.

Invite *invite = (Invite *)[NSEntityDescription insertNewObjectForEntityForName:@"Invite" 
                                                        inManagedObjectContext:anotherContext];

[invite setTitle:[inviteDetailsModel descriptionOfInvite]];

GuestList *guestlist = [NSEntityDescription insertNewObjectForEntityForName:@"GuestList" 
                                                           inManagedObjectContext:anotherContext];
[guestlist setGuestlist_to_invite:invite];
[guestlist setDateInvited:[NSDate date]];

for (Invitee *invitee in [inviteDetailsModel peopleInvited]) {

        Guest *guest = [NSEntityDescription insertNewObjectForEntityForName:@"Guest" 
                                                                  inManagedObjectContext:anotherContext];
        [guest setFirstName:invitee.firstName];
        [guest setLastName:invitee.lastName];
        [guest setABookID:invitee.guestID];

        [guestlist addGuestObject:guest];
    }
}

[invite setGuestlist:guestlist];

NSError *error = nil;
if(![anotherContext save:&error]) {
    NSLog(@"Couldnt save our invite data %@",error);
    return nil;
}

Answer 1

If guest list has a one to many relationship with guest then guest can connect to only one guest list. In practice that means only the last guest list you assign to it (whether implicitly or explicitly) will stick.

You want to change that relationship to many to many.