Populate TableView from CoreData with NSFetchRequest - swift

Question

I need to populate my table view with the data from my core data.
I can display my rows but, I can't populate my tableview!
I use Swift 3 and Xcode 8.
This is my code, in this controller I have to display the list.
class iTableViewController: UITableViewController, NSFetchedResultsControllerDelegate{
#IBOutlet var iTableView: UITableView!
override func viewDidLoad(){
super.viewDidLoad()
iTableView.dataSource = self
iTableView.delegate = self
let appDelegate = UIApplication.shared.delegate as! AppDelegate
let managerContext = appDelegate.persistentContainer.viewContext
let interventsFetch = NSFetchRequest<NSFetchRequestResult>(entityName: "Intervento")
do{
//results
let fetchedIntervents = try managerContext.fetch(interventsFetch) as! [Intervento]
for interv in fetchedIntervents{
print(interv.stampRow())
}
NSLog(String(fetchedIntervents.count))
}catch{
fatalError("Failed to fetch employees: \(error)")
}
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
//number of sections
override func numberOfSections(in tableView: UITableView) -> Int {
return 1
}
//numer of rows
override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return 1
}
//cell
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell: UITableViewCell = UITableViewCell(style: UITableViewCellStyle.subtitle, reuseIdentifier: "cell")
cell.accessoryType = UITableViewCellAccessoryType.disclosureIndicator
//print the example cell
cell.textLabel?.text = "title"
cell.detailTextLabel?.text = "subtitle"
return cell
}
//swipe and delete
override func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath: IndexPath){
if(editingStyle == UITableViewCellEditingStyle.delete){
//TODO
}
}
// click cell
override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath){
performSegue(withIdentifier: "segueDetail", sender: self)
}
override func viewDidAppear(_ animated: Bool){
//iTableView.reloadData()
}
override func viewWillDisappear(_ animated: Bool) {
//iTableView.reloadData()
//fetchData()
}
}
this is my class
extension Intervento {
#nonobjc public class func fetchRequest() -> NSFetchRequest<Intervento> {
return NSFetchRequest<Intervento>(entityName: "Intervento");
}
#NSManaged public var cliente: Int32
#NSManaged public var dataFine: String?
#NSManaged public var dataInizio: String?
#NSManaged public var descrizione: String?
#NSManaged public var foto: String?
#NSManaged public var id: Int32
#NSManaged public var stato: String?
#NSManaged public var tecnico: String?
func stampRow()->String{
let v1 = String(id) + " " + String(cliente) + " "
let v2 = dataInizio! + " " + dataFine! + " "
let v3 = stato! + " " + tecnico! + " " + descrizione!
return v1 + v2 + v3
}
}
and this is the my code for save the data (it works)
#IBAction func addButton(_ sender: Any){
//genero la data
let dateFormatter = DateFormatter()
dateFormatter.dateFormat = "dd-MM-yyyy HH:mm"
let strDate = dateFormatter.string(from: myDatePicker.date)
let appDelegate = UIApplication.shared.delegate as! AppDelegate
let managerContext = appDelegate.persistentContainer.viewContext
let newInt = NSEntityDescription.insertNewObject(forEntityName: "Intervento", into: managerContext)
newInt.setValue(1, forKey: "id")
newInt.setValue(strDate, forKey: "dataInizio")
newInt.setValue("", forKey: "dataFine")
newInt.setValue(2, forKey: "cliente")
newInt.setValue("Matt", forKey: "tecnico")
newInt.setValue(stato[1], forKey: "stato")
newInt.setValue("", forKey: "descrizione")
newInt.setValue("", forKey: "foto")
do{
try managerContext.save()
print("saved")
}catch let error as NSError{
//errore salvataggio
print("Could not fetch \(error), \(error.userInfo)")
}
}

Answer 1

First of all, your class should implement this protocols:
UIViewController, UITableViewDataSource, UITableViewDelegate, NSFetchedResultsControllerDelegate
You can load data from a persistent storage with this code:
//load data
//persistant container
let persistentContainer = NSPersistentContainer.init(name: "Model")
//
lazy var fetchedResultsController: NSFetchedResultsController<Intervento> = {
// Create Fetch Request
let fetchRequest: NSFetchRequest<Intervento> = Intervento.fetchRequest()
// Configure Fetch Request
fetchRequest.sortDescriptors = [NSSortDescriptor(key: "dataInizio", ascending: false)]
let appDelegate = UIApplication.shared.delegate as! AppDelegate
let managerContext = appDelegate.persistentContainer.viewContext
// Create Fetched Results Controller
let fetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: managerContext, sectionNameKeyPath: nil, cacheName: nil)
// Configure Fetched Results Controller
fetchedResultsController.delegate = self
return fetchedResultsController
}()
//carica
func load(){
//persistant container
persistentContainer.loadPersistentStores { (persistentStoreDescription, error) in
if let error = error {
print("Unable to Load Persistent Store")
print("\(error), \(error.localizedDescription)")
} else {
do {
try self.fetchedResultsController.performFetch()
} catch {
let fetchError = error as NSError
print("Unable to Perform Fetch Request")
print("\(fetchError), \(fetchError.localizedDescription)")
}
}
}
}
override func viewDidLoad(){
super.viewDidLoad()
iTableView.delegate = self
iTableView.dataSource = self
// trigger load
load()
}
Your data will be fetched and will show up because you have delegated iTableViewController by this line of code:
// Configure Fetched Results Controller
fetchedResultsController.delegate = self
In order to make this work, your ViewController must conform to NSFetchedResultsControllerDelegate protocol, here you can find a possibile implementation:
extension iTableViewController: NSFetchedResultsControllerDelegate {
func controllerWillChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
iTableView.beginUpdates()
}
func controllerDidChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
iTableView.endUpdates()
}
func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange anObject: Any, at indexPath: IndexPath?, for type: NSFetchedResultsChangeType, newIndexPath: IndexPath?) {
switch (type) {
case .insert:
if let indexPath = newIndexPath {
iTableView.insertRows(at: [indexPath], with: .fade)
}
break;
case .delete:
if let indexPath = indexPath {
iTableView.deleteRows(at: [indexPath], with: .fade)
}
break;
case .update:
if let indexPath = indexPath, let cell = iTableView.cellForRow(at: indexPath) {
configureCell(cell, at: indexPath)
}
break;
case .move:
if let indexPath = indexPath {
iTableView.deleteRows(at: [indexPath], with: .fade)
}
if let newIndexPath = newIndexPath {
iTableView.insertRows(at: [newIndexPath], with: .fade)
}
break;
}
}
}
In conclusion, this is the full implementation of your iTableViewController (I have included also the necessary code for deleting an row):
class iTableViewController: UIViewController, UITableViewDataSource, UITableViewDelegate{
#IBOutlet var iTableView: UITableView!
//load data
//persistant container
let persistentContainer = NSPersistentContainer.init(name: "Model")
//
lazy var fetchedResultsController: NSFetchedResultsController<Intervento> = {
// Create Fetch Request
let fetchRequest: NSFetchRequest<Intervento> = Intervento.fetchRequest()
// Configure Fetch Request
fetchRequest.sortDescriptors = [NSSortDescriptor(key: "dataInizio", ascending: false)]
let appDelegate = UIApplication.shared.delegate as! AppDelegate
let managerContext = appDelegate.persistentContainer.viewContext
// Create Fetched Results Controller
let fetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: managerContext, sectionNameKeyPath: nil, cacheName: nil)
// Configure Fetched Results Controller
fetchedResultsController.delegate = self
return fetchedResultsController
}()
//carica
func load(){
//persistant container
persistentContainer.loadPersistentStores { (persistentStoreDescription, error) in
if let error = error {
print("Unable to Load Persistent Store")
print("\(error), \(error.localizedDescription)")
} else {
do {
try self.fetchedResultsController.performFetch()
} catch {
let fetchError = error as NSError
print("Unable to Perform Fetch Request")
print("\(fetchError), \(fetchError.localizedDescription)")
}
}
}
}
override func viewDidLoad(){
super.viewDidLoad()
iTableView.delegate = self
iTableView.dataSource = self
// trigger load
load()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
//numero di sezioni
func numberOfSections(in tableView: UITableView) -> Int {
return 1
}
//numero di righe
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
guard let quotes = fetchedResultsController.fetchedObjects else { return 0 }
return quotes.count
}
//gestisco la cella
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
//genero la cella
let cell: UITableViewCell = UITableViewCell(style: UITableViewCellStyle.subtitle, reuseIdentifier: "cell")
configureCell(cell, at:indexPath)
return cell
}
//swipe and delete
func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath: IndexPath){
if(editingStyle == .delete){
// Fetch Quote
let quote = fetchedResultsController.object(at: indexPath)
// Delete Quote
quote.managedObjectContext?.delete(quote)
}
}
// click cell
func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath){
performSegue(withIdentifier: "segueDetail", sender: self)
}
func configureCell(_ cell: UITableViewCell, at indexPath: IndexPath) {
//get intervento
let intervento = fetchedResultsController.object(at: indexPath)
//fill the cell
cell.textLabel?.text = intervento.dataInizio
cell.detailTextLabel?.text = "SOME_THING"
}
//quando appare aggiorno la table view
override func viewDidAppear(_ animated: Bool){
self.iTableView.reloadData()
}
}
extension iTableViewController: NSFetchedResultsControllerDelegate {
func controllerWillChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
iTableView.beginUpdates()
}
func controllerDidChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
iTableView.endUpdates()
}
func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange anObject: Any, at indexPath: IndexPath?, for type: NSFetchedResultsChangeType, newIndexPath: IndexPath?) {
switch (type) {
case .insert:
if let indexPath = newIndexPath {
iTableView.insertRows(at: [indexPath], with: .fade)
}
break;
case .delete:
if let indexPath = indexPath {
iTableView.deleteRows(at: [indexPath], with: .fade)
}
break;
case .update:
if let indexPath = indexPath, let cell = iTableView.cellForRow(at: indexPath) {
configureCell(cell, at: indexPath)
}
break;
case .move:
if let indexPath = indexPath {
iTableView.deleteRows(at: [indexPath], with: .fade)
}
if let newIndexPath = newIndexPath {
iTableView.insertRows(at: [newIndexPath], with: .fade)
}
break;
}
}
}
Don't forget to use always the same context when you make operations with your data (for example when you add new data).
let appDelegate = UIApplication.shared.delegate as! AppDelegate
let managerContext = appDelegate.persistentContainer.viewContext
For a full example you should look here: https://github.com/bartjacobs/ExploringTheFetchedResultsControllerDelegateProtocol

Answer 2

Swift 3.3
lazy var fetchedResultsController: NSFetchedResultsController<SavedContact> = {
let fetchReqest: NSFetchRequest<SavedContact> = SavedContact.fetchRequest()
fetchReqest.sortDescriptors = [NSSortDescriptor(key: "id", ascending: true)]
let fetchedResultsController = NSFetchedResultsController(fetchRequest: fetchReqest, managedObjectContext: Database.shared.mainManagedObjectContext, sectionNameKeyPath: nil, cacheName: nil)
fetchedResultsController.delegate = self
return fetchedResultsController
}()
override func viewDidLoad() {
super.viewDidLoad()
self.performFetch()
}
func performFetch() {
do {
try self.fetchedResultsController.performFetch()
} catch {
Debug.Log(message: "Error in fetching Contact \(error)")
}
}
//MARK: - NSFetchResultcontrollerDelegate
extension YourViewC: NSFetchedResultsControllerDelegate {
func controllerDidChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
self.tableView.reloadData()
}
}
// Database Class
private let _singletonInstance: Database = Database()
class Database: NSObject {
class var shared: Database {
return _singletonInstance
}
override init() {
super.init()
}
// Main Managed Object Context
lazy var mainManagedObjectContext: NSManagedObjectContext = {
let coordinator = self.persistentStoreCoordinator
var mainManagedObjectContext = NSManagedObjectContext(concurrencyType: .mainQueueConcurrencyType)
mainManagedObjectContext.persistentStoreCoordinator = coordinator
return mainManagedObjectContext
}()
// Persistent Store Coordinator
lazy var persistentStoreCoordinator: NSPersistentStoreCoordinator = {
let mOptions = [NSMigratePersistentStoresAutomaticallyOption: true,
NSInferMappingModelAutomaticallyOption: true]
let coordinator = NSPersistentStoreCoordinator(managedObjectModel: self.managedObjectModel)
let url = self.applicationDocumentsDirectory.appendingPathComponent("AppName.sqlite")
var failureReason = "There was an error creating or loading the application's saved data."
do {
try coordinator.addPersistentStore(ofType: NSSQLiteStoreType, configurationName: nil, at: url, options: mOptions)
} catch {
// Report any error we got.
var dict = [String: AnyObject]()
dict[NSLocalizedDescriptionKey] = "Failed to initialize the application's saved data" as AnyObject?
dict[NSLocalizedFailureReasonErrorKey] = failureReason as AnyObject?
dict[NSUnderlyingErrorKey] = error as NSError
let wrappedError = NSError(domain: "YOUR_ERROR_DOMAIN", code: 9999, userInfo: dict)
abort()
}
return coordinator
}()
// DB Directory and Path
lazy var applicationDocumentsDirectory: URL = {
let urls = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
let documentDirectoryURL = urls[urls.count - 1] as URL
let dbDirectoryURL = documentDirectoryURL.appendingPathComponent("DB")
if FileManager.default.fileExists(atPath: dbDirectoryURL.path) == false{
do{
try FileManager.default.createDirectory(at: dbDirectoryURL, withIntermediateDirectories: false, attributes: nil)
}catch{
}
}
return dbDirectoryURL
}()
}