Core Data: Execute a fetch request

SomeImplementation.m

NSManagedObjectContext *managedObjectContext = ...;
NSFetchRequest *fetchRequest = ...;

NSError *error = nil;
NSArray *results = [managedObjectContext executeFetchRequest:request error:&error];
if (error) {
    NSLog(@"Error: %@\n%@", [error localizedDescription], [error userInfo]);
    return;
}