Question

I’m simplifying this for my question, but, as an example, let’s say I have a model with an entity named Employee and a Boolean attribute named vacationing which is non-optional but has a default value of NO set.

However, I’m seeing “vacationing is a required value” when attempting to save an update to an Employee entity. The code looks like this:

- (void)reinstateEmployee:(Employee*)employee context:(NSManagedObjectContext*)context {
    employee.vacationing = NO;

    NSError *error;
    if (![context save:error]) {
        NSLog(@"Error saving: %@", error.localizedDescription);
    }
}

Answer 1

The problem here is that NO is really just an alias for 0 which also represents nil and NULL.

Since it’s perfectly valid to assign nil to an NSNumber property, the compiler does not complain and instead of setting vacationing to false, it unsets it, which is not valid when the attribute is required.

This is more obvious by replacing NO with YES, which will produce a compiler warning.

To fix the issue, replace NO with @NO or [NSNumber numberWithBool:NO] to instead assign an NSNumber instance.