Question

I’ve got a little function where I query objects through a relationship in my Core Data model.

I have the to-many side of the relationship all setup. However, I cannot figure out how to properly set the singular side of the relationship as it’s considered an NSSet, and I have no idea what to do with that.

I’ve tried putting objects within an NSSet that I would like to assign to the other “to-many” entity, but that returned an error.

I tried looking through the documentation, and the only examples I found were for a many-many relationship.

I tried searching on SO a little, and couldn’t find anyone who had asked this specific question.

Hopefully somebody out there can understand what I’m asking for, and help me out!

EDIT:

To help you all visualize, I have set the “shindys” side of the relationship, but now I’m trying to set the “user” side, which, as you can see, is a singular relationship.

EDIT:

After @Mundi’s answer below, I have this as my data model:

That all is correct, I just need to have the ability to fetch all of the user’s friends shindy’s along with their own. You could compare this to Twitter’s home feed.

Answer 1

It seems to me that you have your data model set up the wrong way.

One user can have many messages. One message has at least two users (from and to). I do not know what a shindy is, but the way you have set it up, one user has only one shindy which can be shared among several users.

If this is correct, you need to change the message part of your data model and either make it many-to-many, or better make two relationships that describe sender and receiver.

Message                       User
  sender <<-------------------->sentMessages
  receivers <<---------------->>receivedMessages

Also, you should rename your user attribute “shindys” to “shindy”, as it is only singular. Now that we know that shindy is a party, you should change that relationship to a many-to-many.

So to sort your users by shindy if there is only one shindy per user (whatever that is, please elucidate us) you would use a sort descriptor like this

[NSSortDescriptor sortDescriptorWithKey:@"shindy.timePosted" ascending:NO];

If, however, you want to filter by shindy (all users belonging to a shindy if there are several) you would have to use a predicate, like this

[NSPredicate predicateWithFormat:@"ANY shindies.profileID = %@", 
                                                someUser.profileID];

or use some other way to identify the shindy.