context.fetch() in swift

let request = NSFetchRequest<NSFetchRequestResult>(entityName: "Users")        //request.predicate = NSPredicate(format: "age = %@", "12")        request.returnsObjectsAsFaults = false        do {            let result = try context.fetch(request)            for data in result as! [NSManagedObject] {               print(data.value(forKey: "username") as! String)          }                    } catch {                        print("Failed")        }