How to initialize a NSFetchedResultsController in iOS 10 Swift 3

Question

I can\'t get my NSFetchedResultsController initialized in iOS 10 using Swift 3 within CoreDataTableViewController from AECoreDataUI.

let request         


        

Answer 1

NSFetchRequest is now a generic. NSFetchedResultsController is a generic too. Therefore, when declaring variables, you have to use a generic declaration, e.g.:

var fetchedResultsController: NSFetchedResultsController<NasaPicture>?

Answer 2

when we need to declare variable, then we have to use a generic declaration please check below code for NSFetchedResultsController in swift 3..

 override func viewDidLoad() {
     super.viewDidLoad()
    do {
        try self.fetchedResultsController.performFetch()
    } catch {
        let fetchError = error as NSError
        print("Unable to Perform Fetch Request")
        print("\(fetchError), \(fetchError.localizedDescription)")
    }

} // MARK: - NSFetchedResultsController

fileprivate lazy var fetchedResultsController: NSFetchedResultsController<UserExistenceOnXMPPCD> = {
    let fetchRequest = NSFetchRequest<UserExistenceOnXMPPCD>(entityName: "UserExistenceOnXMPPCD")
    fetchRequest.sortDescriptors = [
        NSSortDescriptor(key: "name", ascending: true)]

    let fetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext:CoreDataController.sharedInstance.managedObjectContext, sectionNameKeyPath: nil, cacheName: nil)

    try! fetchedResultsController.performFetch()
    fetchedResultsController.delegate = self
    if let quotes = fetchedResultsController.fetchedObjects {
        if quotes.count > 0 {
            print(quotes.count)
        }
    }
    return fetchedResultsController
}()


// MARK: - NSFetchedResultsController delegate methods
func controllerWillChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>)  {
    tableView.beginUpdates()
}

func controllerDidChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>)  {
    tableView.reloadData()
}

Answer 3

Simply call the function:

private func setupFetchedResultsController() {

    let context = NSManagedObjectContext.mr_default()
    let fetchRequest = NSFetchRequest<Month>(entityName: "Month")
    let dateDescriptor = NSSortDescriptor(key: "date", ascending: false)

    fetchRequest.sortDescriptors = [dateDescriptor]

    fetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: context, sectionNameKeyPath: "year", cacheName: nil)
    fetchedResultsController.delegate = self

    try! fetchedResultsController.performFetch()
    tableView.reloadData()
}