NSPredicate aggregate IN statement not working

Question

I am a bit of a CoreData noob but am slowly getting my head around it. I am having trouble with the following code:

NSArray * artisteIds = [@"1,2,3,4" componentsSeparatedByString:@","];
predicate = [NSPredicate predicateWithFormat:@"(artisteId IN %@)", artisteIds]; 

My Artiste managed object has a NSNumber field of artisteId and I have looped through all Artistes in my object context and there are definately objects with id's 1-420.

But my helper method always returns a empty result set with that query

NSMutableArray* mutableFetchArtistes = [CoreDataHelper searchObjectsInContext:@"Artiste" :predicate :@"title" :YES :managedObjectContext];      

Any suggestions?

To test it works I used the following and got a count of 3 results

predicate = [NSPredicate predicateWithFormat:@"(artisteId = 1) or (artisteId = 2) or (artisteId = 3)", artisteIds];

Answer 1

I think the array artisteIds should contain NSNumber objects, e.g.

NSArray *artisteIds = [NSArray arrayWithObjects:
    [NSNumber numberWithInteger:1],
    [NSNumber numberWithInteger:2],
    [NSNumber numberWithInteger:3],
    [NSNumber numberWithInteger:4],
    nil];

You could also use NSSet rather than NSArray, but I'm not sure if it makes a difference.