On an array of Artists I am trying to do filteredArrayUsingPredicate using the below format to only remain with Artists that have at least one Album that has at least one Intro song.
albums is a to many relationship from Artist to Album. intros is a to many relationship from Album to Intro. I get an exception saying [NSMutableSet unionSet:]: set argument is not an NSSet. What am I doing wrong? Here is the aforementioned predicate format:
@"SUBQUERY(albums, $alb, ANY $alb.intros != NULL).@count != 0"