Core Data predicate for any row of the associated entity

Question

In the following I will describe a simplification of my Core Data schema that I am pretty sure to be equivalent to my real situation.

I have two entity First and Second linked by a many-to-many relationship r.

Second has got two Boolean attribute, let us call it take and you_should_not_take. I want to make a query that select a row of First iff it exits an associated row of Second for with take = true.

I have tried this predicate:

NSPredicate(format: "ANY (%K == YES && %K == NO)", "r.take","r.you_should_not_take")

but Core Data gives me the following error: "[General] Unable to parse the format string".

Maybe I have to use this:

NSPredicate(format: "((ANY %K == YES) && (ANY %K == NO))", "r.take","r.you_should_not_take")

but I am afraid that this last query will select a row of First iff it exists a row x of Second for which x.take == YES && it exists a row y if Second for which y.you_should_not_take == NO, with no guarantee that x == y.

An SQL query would be very simple to be made, but I am not so experienced with Core Data, so while I will try some more queries (and I will test if the second query does what I think it does) I have also asked here hoping the answer would be as simple as in SQL.

Answer 1

To select all First objects which are related to (at least one) Second object for which take==true and you_should_not_take==false you have to use a SUBQUERY. Something like (untested):

SUBQUERY(r, $x, $x.take == YES AND $x.you_should_not_take == NO).@count > 0