NSMutableArray removeObjectAtIndex: throws invalid argument exception

Question

I\'m writing an application to show some news from a portal. The news are fetched using a JSON file from the Internet and then stored into a NSMutableArray using the CoreDat

Answer 1

Your NewsFetcher returns you an immutable array, not a mutable instance. Use the following instead for initialization:

NSArray *results = [[NewsFetcher sharedInstance] 
                     fetchManagedObjectsForEntity:@"News" 
                     withPredicate:predicate
                     withDescriptor:@"Titolo"];
dataSet = [results mutableCopy];

An expression like A *a = (A*)b; only casts the pointer to a different type - it doesn't convert/change the actual type of the instance it points to.