Is there a way to "Reverse" an NSPredicate

Question

Let's say that I have this predicate:

NSPredicate *filter = [NSPredicate predicateWithFormat:@"%K == NO", @"someAttribute"];

And I wish to reverse that predicate to :

NSPredicate *filter = [NSPredicate predicateWithFormat:@"%K == YES", @"someAttribute"];

Is there a way to do this without creating a new predicate.

Answer 1

You can't modify an existing NSPredicate. But you can very easily create a new predicate that is the “reverse” (or more precisely, the negation) of filter:

NSPredicate *notFilter = [NSCompoundPredicate notPredicateWithSubpredicate:filter];

See the +[NSCompoundPredicate notPredicateWithSubpredicate:] documentation.