Quick Explanation of SUBQUERY in NSPredicate Expression

Question

There appears to be zero documentation about the SUBQUERY keyword from Apple and I can\'t find a simple explanation about it on SO or on Google. It\'s a conspiracy! ;)

Answer 1

This is what a subquery evaluates to. (Found from this mailing list thread, the #1 hit for “NSPredicate subquery” in Google.) That bit of documentation also explains how the predicate format string syntax relates to it.