Question

I have an entity which looks like this:

Entityname = Country

with the attributes “city” and “person”.

Country *country = [NSEntityDescription insertNewObjectForEntityForName:@"Country" inManagedObjectContext:context];


    country.city = @"New York";
    country.person = @"Doug";
    country.person = @"Carry";
    country.person = @"Arthur";

I want to save more then one people in that City.

I am using the code posted above, but only the last person is saved.

How I can save more then one people in CoreData?

Hope you can help me.

Answer 1

An approach for solving your problem would be:

1. Create 3 Entities: Country, City and Person
2. Setup the properties for your entities (e.g. Country.name, City.name, Person.name etc) using the graphical tool of XCode
3. Setup the relations between your Entities. You need a one-to-many from Country -> City [call it cities] and a one-to-many from City -> Person [call it persons] (See Apple’s documentation regarding this subject). Keep in mind that you will need to set the inverse relations as well.
4. That’s where all the fun begins… Choose Editor > Create NSManagedObject subclass. Xcode then will generate the files based on your model. Now if you look at the header files, you should see among the generated methods something similar to this:

…

- (void)addPersonObject:(Person *)value;
- (void)removePersonObject:(Person *)value;
- (void)addPersons:(NSSet *)value;
- (void)removePersons:(NSSet *)value;

…

From this point is quite obvious to figure out how to add multiple objects 🙂
I know that all this may seem hard at first but once you get yourself into this you will really be able to manage complex object graphs easy and efficiently.
I hope that this information will set you on the right track!