iOS: core data update object with one- with to-many relationship

Question

In my app I have this code to update a DB:

NSManagedObjectContext *context = [self managedObjectContext];

NSFetchRequest *fetchRequest=[NSFetchRequest fetchRequestWithEntityName:@"Struct"];
        NSError *error = nil;

        for (id element in array){
            [fetchRequest setPredicate:[NSPredicate predicateWithFormat:@"id==%@",[element objectForKey:@"id"]]];

            Struct *struct = [[context executeFetchRequest:fetchRequest error:&error] lastObject];

            if (struct != nil){
                //updating value of attributes
                struct.name = [element objectForKey:@"n"];
                struct.val = [element objectForKey:@"val"];
                struct.pos = [element objectForKey:@"pos"];


            }
             else{
              //create a new identity
             }
         }

it's all ok but I have other two objects in relationship with Struct:

"Id_Loc" (one to many) "Details" (one to one)

I don't know how to update them, I don't know how to call them from my object 'Struct' I don't find nothing Can you help me? thanks

`Struct` should have some methods in the header (show that code). Do the relationships already contain objects to be updated, or you need to add new ones? How about deleting any existing ones? — Wain, Feb 25 '14 at 15:43

score 3 · Accepted Answer · answered Feb 25 '14 at 15:44

It works the same way you're using .name, .val and .pos.

The one-to-one relationship will return an object, the one-to-many relationship will return a NSSet.

Say your one-to-one relationship is from Struct to Bar and the relationship name is bar, you'll receive a Bar object by using struct.bar.

Edit: If you want to add new objects to the one-to-many relationship you should use [struct addFooObject:]; where Foo is your objects name.

iOS: core data update object with one- with to-many relationship

1 Answers1