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

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 is NOT set. I tried using a predicate like this:

NSPredicate *predicate = [NSPredicate predicateWithFormat: @"(date = NIL)"];

But I still get objects where the date is set. What is the right way to set up a predicate for this?

I think it's a case sensitivity issue. You can use "nil" or "NULL", but not "NIL". This works fine for me:

NSPredicate *eventWithNoEndDate = [NSPredicate predicateWithFormat:@"endDate = nil"];

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"]];

https://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/Predicates/Articles/pUsing.html#//apple_ref/doc/uid/TP40001794-SW4

following code should work

predicate = [NSPredicate predicateWithFormat:@"firstName = nil"];