Question

I am using the core data in my application.
I know how to insert a new object into it.which stores songs information into it.
below is my table sturcture

song_id

song_title

song_description

Songs *aSong = (Poem *)[NSEntityDescription insertNewObjectForEntityForName:@"Songs" inManagedObjectContext:myManagedObjectContext];  

here i want to know how to check whether the song_id is already available before inserting the object again inside the table.

i mean before inserting the new object, how can i check for existence of it.

also how to check the table is empty?

Pls let me know and thanks

Answer 1

NSError * error;
NSFetchRequest * checkExistance = [[NSFetchRequest alloc] init];
[checkExistance setEntity:[NSEntityDescription entityForName:NSStringFromClass([yourClass class]) inManagedObjectContext:yourManagedContext]];
[checkExistance setFetchLimit:1];
[checkExistance setPredicate:[NSPredicate predicateWithFormat:@"ID == %@", yourID]];
Songs *yourSong = [[managedObjectContext executeFetchRequest:checkExistance error:&error] lastObject];

now here if yourSong exists i.e. not null than it id exists.

Hope this helps.