Delete record from core data not working?

Question

I am working with core data, when I deleting record from DB it's not working. Entity name : Entity Attributes : id, date, title

- (void) getData {

NSFetchRequest * fetReq = [NSFetchRequest fetchRequestWithEntityName:@"Entity"];
NSError * fetchErrorObj;
NSArray *result = [self.ad.managedObjectContext executeFetchRequest:fetReq error:&fetchErrorObj];

NSLog(@"array count is %lu", result.count);

NSMutableArray *idArr = [[NSMutableArray alloc]init];
NSMutableArray *titleArr = [[NSMutableArray alloc]init];
NSMutableArray *dateArr = [[NSMutableArray alloc]init];

for (int i=0; i<result.count; i++) {

    self.storedManagedObj = [result objectAtIndex:i];

    [idArr addObject:[self.storedManagedObj valueForKey:@"id"]];
    [titleArr addObject:[self.storedManagedObj valueForKey:@"title"]];
    [dateArr addObject:[self.storedManagedObj valueForKey:@"date"]];

}
self.idArray = sidArr;
}

To delete record...

- (IBAction)deleteRecord:(UIButton *)sender {

NSNumber *value=[NSNumber numberWithInt:[[self.idArray objectAtIndex:0] intValue]];
NSLog(@"%@", [self.idArray objectAtIndex:0]);
NSFetchRequest *request = [[NSFetchRequest alloc] initWithEntityName:@"Entity"];
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"id == %@", value];
NSLog(@"predicate :%@", predicate);
[request setPredicate:predicate];
NSLog(@"request :%@", request);
NSError *error = nil;
NSArray *result = [self.ad.managedObjectContext executeFetchRequest:request error:&error];
NSLog(@"result: %@", result);
if (!error && result.count > 0) {
    for(NSManagedObject *managedObject in result){
        NSLog(@"managedObject :%@", managedObject);
        [self.ad.managedObjectContext deleteObject:managedObject];
    }

    //Save context to write to store
    [self.ad.managedObjectContext save:nil];
}


}

I am getting result like this predicate :id == 38 request : (entity: Entity; predicate: (id == 38); sortDescriptors: ((null)); type: NSManagedObjectResultType; ) result :( )

Sandeep Bhandari · Accepted Answer · 2017-10-04T07:20:50.107

1

The error is pretty clear. It states that you need to specify SortDescriptor to your FetchRequest

    NSFetchRequest *request = [[NSFetchRequest alloc] initWithEntityName:@"Entity"];
    NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"<#Sort key#>"
                                                                   ascending:YES];
    request.sortDescriptors = @[sortDescriptor];

OR

NSArray *sortDescriptors = [[NSArray alloc] initWithObjects: sortDescriptor, nil];
[request setSortDescriptors:sortDescriptors];

Read : NSFetchRequest without sort descriptors

EDIT:

As OP isn't concerned about sorting the result in any specific order and the question lacks the description of entity and the only field that I can see in question is id updating my answer to use id in sort descriptor field

[[NSSortDescriptor alloc] initWithKey:@"id" ascending:YES];

EDIT 2:

NSFetchRequest *request = [[NSFetchRequest alloc] initWithEntityName:@"Entity"];
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"id == %@", [self.idArray objectAtIndex:0]];

Issue in the code was :

NSNumber *value=[NSNumber numberWithInt:[[self.idArray objectAtIndex:0] intValue]];

OP was trying to create a NSNumber from an object in self.idArray using intValue which means idArray is a array of String and not NSNumber. That means id is saved as String in core data and not as NSNumber.

In predicate however OP was trying to pass NSNumber to compare with id. Since id is String and passed argument is NSNumber comparison was failing hence was not returning any objects.

edited Oct 04 '17 at 07:20

answered Oct 04 '17 at 06:38

Sandeep Bhandari

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Bro what is sort key – Naresh Oct 04 '17 at 06:39
@ios-developer : Name of the field in Entity based on which results needs to be sorted. Because in your case sorting isn't important specify any field in Entity like name – Sandeep Bhandari Oct 04 '17 at 06:40
you can specify key as "id" – Sandeep Bhandari Oct 04 '17 at 06:44
NSNumber *value=[NSNumber numberWithInt:[[self.idArray objectAtIndex:0] intValue]]; NSLog(@"%@", [self.idArray objectAtIndex:0]); NSFetchRequest *request = [[NSFetchRequest alloc] initWithEntityName:@"Entity"]; NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"id" ascending:YES]; request.sortDescriptors = @[sortDescriptor]; NSPredicate *predicate = [NSPredicate predicateWithFormat:@"id == %@", value]; NSLog(@"predicate :%@", predicate); [request setPredicate:predicate]; NSLog(@"request :%@", request); But the result in empty – Naresh Oct 04 '17 at 06:45
@ios-developer : Whats the issue buddy ?? – Sandeep Bhandari Oct 04 '17 at 06:46
Are you sure NSArray *result = [self.ad.managedObjectContext executeFetchRequest:request error:&error]; returning array – Sandeep Bhandari Oct 04 '17 at 06:49
Yes, it's returning array. – Naresh Oct 04 '17 at 06:50
Whats the count of it ?? – Sandeep Bhandari Oct 04 '17 at 06:51
result.count = 0; – Naresh Oct 04 '17 at 06:52
@ios-developer : if the count is 0 that means there is no entity in core data matching your predicate so how will it delete anything buddy ?? Control will never enter for loop – Sandeep Bhandari Oct 04 '17 at 06:53
But I am getting request like this, request : (entity: Entity; predicate: (id == 37); sortDescriptors: (( "(id, ascending, compare:)" )); type: NSManagedObjectResultType; ) – Naresh Oct 04 '17 at 06:57
@ios-developer : The only issue in code I have told you the fix So code is fine now. When u call getData you sure there is a entity with id = 37 ??? – Sandeep Bhandari Oct 04 '17 at 06:58
Yes, this is my array...id = ( 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48 ) – Naresh Oct 04 '17 at 06:59
@ios-developer : Gimme a moment lemme check – Sandeep Bhandari Oct 04 '17 at 07:04
@ios-developer : Can you use the code in my Edit 2 Ill tell you whats wrong if my code works – Sandeep Bhandari Oct 04 '17 at 07:07
@ios-developer : Am glad I could be of help :) Happy coding – Sandeep Bhandari Oct 04 '17 at 07:10
Let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/155877/discussion-between-sandeep-bhandari-and-ios-developer). – Sandeep Bhandari Oct 04 '17 at 07:11
@ios-developer : Updated answer with reason for failure of predicate for future references – Sandeep Bhandari Oct 04 '17 at 07:21

Delete record from core data not working?

1 Answers1