ios Core data bug with predicate

Question

I have some strange behaviour with my Core Data.

I have entity Card, that have NSNumber property idObject

When I want to change some info in this card, I try find similar card in my CoreData, but sometimes it work, and sometimes not. I mean next:

NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Card"];
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"idObject == %@", objectId];
request.predicate = predicate;
NSError *error;
NSArray *objects = [self.backgroundManagedObjectContext executeFetchRequest:request error:&error];

Sometimes this code return objects array, but sometimes it return nil. I add next code after previous part of code:

request.predicate = nil;
NSArray *cards = [self.backgroundManagedObjectContext executeFetchRequest:request error:nil];

Error always nil, so all must be fine. And cards array has Card with idObject, that I try to find. So finally if we try execute next code several times:

NSLog(@"idObject -%@-", objectId);
NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Card"];
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"idObject == %@", objectId];
request.predicate = predicate;
NSError *error;
NSArray *objects = [self.backgroundManagedObjectContext executeFetchRequest:request error:&error];
NSLog(@"objects count = %i", objects.count);
request.predicate = nil;
NSArray *cards = [self.backgroundManagedObjectContext executeFetchRequest:request error:nil];
NSLog(@"\nCards:");
for (Card *card in cards) {
    NSLog(@"id -%@-", card.idObject);
}

So we have next results. In first time you can see next:

2014-03-10 11:58:47.115[4397:6613] idObject -1-
2014-03-10 11:58:47.127[4397:6613] objects count = 1
2014-03-10 11:58:47.134[4397:6613] 
Cards:
2014-03-10 11:58:47.145[4397:6613] id -5-
2014-03-10 11:58:47.146[4397:6613] id -4-
2014-03-10 11:58:47.148[4397:6613] id -1-
2014-03-10 11:58:47.148[4397:6613] id -2-
2014-03-10 11:58:47.149[4397:6613] id -6-
2014-03-10 11:58:47.150[4397:6613] id -8-
2014-03-10 11:58:47.151[4397:6613] id -7-
2014-03-10 11:58:47.152[4397:6613] id -3-

In second it return me:

2014-03-10 11:59:42.752[4397:9e2b] idObject -1-
2014-03-10 11:59:42.758[4397:9e2b] objects count = 0
2014-03-10 11:59:42.761[4397:9e2b] 
Cards:
2014-03-10 11:59:42.762[4397:9e2b] id -1-
2014-03-10 11:59:42.764[4397:9e2b] id -5-
2014-03-10 11:59:42.766[4397:9e2b] id -2-
2014-03-10 11:59:42.768[4397:9e2b] id -6-
2014-03-10 11:59:42.769[4397:9e2b] id -8-
2014-03-10 11:59:42.771[4397:9e2b] id -3-
2014-03-10 11:59:42.773[4397:9e2b] id -4-
2014-03-10 11:59:42.775[4397:9e2b] id -7-

So I have in cards array always Card with such idObject, but why with my predicate, it sometimes return me that card and sometimes no? What's wrong?

Answer 1

In Card entity property idObject is type of NSNumber, change idObject in predicate to NSNumber ie.

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"idObject == %@", [NSNumber numberWithInt:[idObject integerValue]]];

or use NSNumberFormatter to change idObject to NSNumber.

Hope this will help you