Core Data Many-to-Many Relationship NSPredicate

Question

I have a data model with a many-to-many relationship like EntityA <-->> EntityB <<--> EntityC. I used to query EntityA with diffe

Answer 1

(I had a lot of trouble puzzling out your predicate so take this with a grain of salt.)

I think your making this overly complicated. You should simplify with keypaths. Each EntityB has a to-one relationship to a EntityC so to search on EntityB objects all you need to do is check EntityB.entityCRelationshipName.entityCAttribute. So something like:

ALL B.EntityC.name like %@

In any case, (if I'm reading the predicate correctly) this:

SUBQUERY($B.EntityC, $EntityC, $EntityC.name like %@)

can only return a single object instead of a collection. Therefore, the predicate will not be able to perform a count on it. That is what your error message means.

I suggest using the predicate editor in the Data Model editor to hash out the predicates before you store them.