core data array as attribute

Question

I want create attribute of "event" entity that will have a short list of events what the correct way to make it? I think the right way is just use array but how can I do it? if someone can give me code example it will be nice.

create one more entity named as `ShortEvent` & use it to point from the original entity `Event` using primary key & foreign key mechanism. — hp iOS Coder, Dec 04 '12 at 12:01
core data is something new for me, I don't understand what you try to tell me can you explain how to use primary key? or link me to tutorial? also I am not sure you understand me as well, I have entity PERSON that will have relation to EVENT that will have type(attribute) when user create new EVENT I just want that he be able choose the type of the event from list (not insert by him self just choose) how do it? — Dennis, Dec 04 '12 at 15:10

score 1 · Accepted Answer · answered Dec 05 '12 at 15:57

Don't listen to any advice regarding foreign keys - they do not exist in Core Data. What you have to do is link your Event entity to another (or itself) with a relationship.

It is not clear why an event would have a short list of events. Maybe you want to distinguish event types or something similar. You could then create a new entity EventType and establish a to-many relationship in the Core Data Model Editor:

Event <<----->> EventType

Now an event could be linked an arbitrary number of EventType objects. You could use a relationship name like allowedEventTypes for each event and access this set (not an array, mind you, but an NSSet with unordered unique objects):

NSSet *types = event.allowedEventTypes;

Once you master the core data modeling technique, the coding becomes exceedingly simple.

core data array as attribute

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