objective c - How to create SourceList to show Core Data ToMany relations? -

coming ios, stuck @ nsoutlineview source list, have read many resources cannot grasp clearly.

what want is, show coredata tomany relationship sourcelist using nstreecontroller. persisting data text file disk. entities , relations follow:

group >> item >> description

sourcelist example:

my app not allow user create new entity, view saved textfile. can nsarraycontroller need show data in single table hierarchy. in nsarraycontroller, needed bind managed object context parameter , and object controller entity name. on tableview needed bind content , selection indexes nsarraycontroller.

how can bind nstreecontroller sourcelist , when children selected, show tomany relation item description.

i can think of 2 solutions , maybe there better one.

solution 1: create subclass of nstreecontroller , override

- (nsstring *)childrenkeypathfornode:(nstreenode *)node 

the managed object node.representedobject.

solution 2: create nsmanagedobject subclasses , implement children method returns child relationship.

- (nsset *)children {     return self.itemsingroup; } 

set childrenkeypath of tree controller 'children'.

i think solution 2 feels wrong, managed objects shouldn't contain code views, easy implement if have nsmanagedobject subclasses.