How to check NSString type DB object is null?

Question

I wanted to fetch only those users who do not have null lastname which of NSString type.

NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"USER" inManagedObjectContext:dbHandler.managedObjectContext];

    NSMutableArray * predicateArray = [[NSMutableArray alloc] init];

    NSPredicate * predicate1 = [NSPredicate predicateWithFormat:@"id = %@",abc];
    [predicateArray addObject:predicate1];

    NSPredicate * predicate2 = [NSPredicate predicateWithFormat:@"lastname != %@",nil];
    [predicateArray addObject:predicate2];

    NSCompoundPredicate * resultantPredicate = [NSCompoundPredicate andPredicateWithSubpredicates:predicateArray];

    [fetchRequest setEntity:entity];
    [fetchRequest setPredicate:resultantPredicate];

    NSError *fetchError = nil;

    NSArray *result = [dbHandler.managedObjectContext executeFetchRequest:fetchRequest error:&fetchError];

Predicate2 is not working for some reason.After applying it no object is returned even if DB contains some Non-Null string values of lastname. Please tell what is wrong in the code or is there any way to fetch not-null string ONLY from core data .

@Divjyot - try the duplicate answer once , if duplicate answer does not resolved ur issue ping here, I reopen ur question again — Anbu.Karthik, Apr 11 '16 at 12:17
will try NSPredicate *predicateName = [NSPredicate predicateWithFormat:@"name!=nil AND name!=' ' "]; — djay, Apr 11 '16 at 12:19
@Anbu.Karthik NO, the original answer had it already mentioned that it will NOT work for CORE DATA..... — djay, Apr 11 '16 at 12:28

score 0 · Answer 1 · edited May 23 '17 at 11:59

0

You can use method which is described here.

Just replace

[NSPredicate predicateWithFormat:@"lastname != %@",nil]

with

[NSPredicate predicateWithFormat:@"lastname.length > 0"]

UPDATE

This predicates will return nil objects

[NSPredicate predicateWithFormat:@"lastname = NULL"];
[NSPredicate predicateWithFormat:@"lastname = NIL"];

This predicate will return empty strings

[NSPredicate predicateWithFormat:@"lastname = ''"];

edited May 23 '17 at 11:59

Community

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answered Apr 11 '16 at 12:07

Che

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.length property is not available in core data and If the string is empty, this will fail (because 0 == 0). Similarly, if name is nil, it will also fail, because [nil length] == 0. as wriiten in http://stackoverflow.com/questions/7369390/nspredicate-to-test-for-null-and-blank-strings – djay Apr 11 '16 at 12:25
So, when user has empty string as 'lastname' will be different case if user has 'nil' as lastname, right? – Che Apr 11 '16 at 12:53
nil can show itself as empty lastname but an empty string @" " is not equal to nil. – djay Apr 11 '16 at 13:07
@Divjyot, I know :) But it depend from your logic. Is logic the same for both cases or not… – Che Apr 11 '16 at 13:44
Let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/108824/discussion-between-divjyot-and-che). – djay Apr 11 '16 at 13:50

How to check NSString type DB object is null?

1 Answers1