How to compare objects in NSPredicate format string

At first round i got object with parent = nil, then i want to get other object with parent equal to previously fetched object, but how i must to design predicate?
this not works:

Code:

parent == 0x1004423e0 and title == 'a leaf'
parent.objectID == (0x100165760 <x-coredata:///Item/tCFB2D3BF-66F2-480A-BBC3-3699C25E70AE2>) and title == 'a leaf'
parent.objectID == 0x100163870 and title == 'a leaf'

but this works

Code:

parent == nil and title == 'root'