How do I set up a NSPredicate to look for objects that have a nil attribute

Question

I have a ManagedObject class, and one of the members of the class is a NSDate. I would like to display all objects of the class for which the date

Answer 1

Figured it out. Couldn't do it by using a predicate with a string format, so tried a predicate with a template and it worked. Here's the code that gave me objects that had endDate set to NULL:

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"endDate = $DATE"];
predicate = [predicate predicateWithSubstitutionVariables:
                   [NSDictionary  dictionaryWithObject:[NSNull null] forKey: @"DATE"]];