nsfetchedresultscontroller with distinct results

nsfc_distinct.swift

let fetchRequest: NSFetchRequest<NSDictionary> = NSFetchRequest(entityName: "Bus")
fetchRequest.propertiesToFetch = ["carreira"]
fetchRequest.returnsDistinctResults = true
fetchRequest.returnsObjectsAsFaults = false
fetchRequest.resultType = NSFetchRequestResultType.dictionaryResultType
fetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: CoreDataManager.sharedManager.mainContext, sectionNameKeyPath: nil, cacheName: nil) as? NSFetchedResultsController<NSFetchRequestResult>
fetchedResultsController?.delegate = nil
do {
        try fetchedResultsController?.performFetch()
} catch {
        fatalError("Unable to perform fetch")
}