to check an coredata object is nil

Question

I want to find out the objects in the core data, my code: Types: `signedDate` (Date) `alarmDate`(Date) `starTime`(NSDate) `endTime`(NSDate) ``` NSString *str = @"(signedDate >= %@) AND (signedDate < %@) AND (alarmDate == nil)"; NSPredicate *predicate = [NSPredicate predicateWithFormat:str, starTime, endTime]; [request setPredicate:predicate]; NSArray *results=[context executeFetchRequest:request error:nil]; ``` predicate is wrong ? How to judge an coredata object is nil? What the predicate should be?

Accepted Answer

I don't think the predicate syntax calls for == nil. Use only one =

```
NSString *str = @"(signedDate >= %@) AND (signedDate < %@) AND (alarmDate = nil)";
```

Your code above works right. It should be YES since it's nil.

```
BOOL ok;
predicate = [NSPredicate predicateWithFormat:@"firstName = nil"];
ok = [predicate evaluateWithObject:[NSDictionary dictionary]];

ok = [predicate evaluateWithObject:
[NSDictionary dictionaryWithObject:[NSNull null] forKey:@"firstName"]]; 
```

to check an coredata object is nil

Solution

Problem