iphone - How can I perform a subquery in Core Data for to-many relationship? -

i did research , cannot find answer simple core data issue.

here simplified object model:

person -->> events event --> date 

what query persons , sort them recent event.

i took @ postings on subquery within predicate. however, don't know how query recent. can't use "event.date" in sort descriptor not allowed since nsset.

some code reference...

nsfetchrequest *fetchrequest = [[nsfetchrequest alloc] init]; nsentitydescription *entity = [nsentitydescription entityforname:@"person" inmanagedobjectcontext:self.managedobjectcontext]; [fetchrequest setentity:entity];  // following errors:     nssortdescriptor *sortdescriptor = [[nssortdescriptor alloc] initwithkey:@"event.date" ascending:no selector:nil]; 

any appreciated.

you approaching problem backwards. should fetch event objects sorted on date , ask each event object related person objects.

you can create subquery predicate event objects can't sort on relationship.