retrieving core data into tableview cells swift

Question

I am trying to simply store and retrieve CoreData (something that I\'ve done successfully before with swift). I was getting a nil for data, but now (not sure what changed) I

Answer 1

When using core data and a tableview, you should use NSFetchedResultsController. This essentially retrieves data from core data and organizes it by section and indexPath so it can easily be set as the data source of the tableView. Here is a complete implementation of a potential UITableViewController that conforms to NSFetchedResultsControllerDelegate:

import Foundation
import UIKit
import CoreData


class HomeViewController: UITableViewController, NSFetchedResultsControllerDelegate {

    let managedObjectContext: NSManagedObjectContext? = (UIApplication.sharedApplication().delegate as? AppDelegate)?.managedObjectContext

    var fetchedResultsController: NSFetchedResultsController?

    override func viewDidLoad() {
        super.viewDidLoad()

        fetchedResultsController = NSFetchedResultsController(fetchRequest: allEmployeesFetchRequest(), managedObjectContext: managedObjectContext!, sectionNameKeyPath: nil, cacheName: nil)
        fetchedResultsController?.delegate = self
        fetchedResultsController?.performFetch(nil)


    }

    func allEmployeesFetchRequest() -> NSFetchRequest {

        var fetchRequest = NSFetchRequest(entityName: "Employee")
        let sortDescriptor = NSSortDescriptor(key: "nameLast", ascending: true)

        fetchRequest.predicate = nil
        fetchRequest.sortDescriptors = [sortDescriptor]
        fetchRequest.fetchBatchSize = 20

        return fetchRequest
    }

    //MARK: UITableView Data Source and Delegate Functions
    override func numberOfSectionsInTableView(tableView: UITableView) -> Int {
        return fetchedResultsController?.sections?.count ?? 0
    }

    override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {

        return fetchedResultsController?.sections?[section].numberOfObjects ?? 0
    }

    override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCellWithIdentifier("HomeCell", forIndexPath: indexPath) as UITableViewCell

        if let cellContact = fetchedResultsController?.objectAtIndexPath(indexPath) as? Employee {
            cell.textLabel?.text = "\(cellContact.nameLast), \(cellContact.nameFirst)"

        }


        return cell
    }

    //MARK: NSFetchedResultsController Delegate Functions
    func controller(controller: NSFetchedResultsController, didChangeSection sectionInfo: NSFetchedResultsSectionInfo, atIndex sectionIndex: Int, forChangeType type: NSFetchedResultsChangeType) {

        switch type {
        case NSFetchedResultsChangeType.Insert:
            tableView.insertSections(NSIndexSet(index: sectionIndex), withRowAnimation: UITableViewRowAnimation.Fade)
            break
        case NSFetchedResultsChangeType.Delete:
            tableView.deleteSections(NSIndexSet(index: sectionIndex), withRowAnimation: UITableViewRowAnimation.Fade)
            break
        case NSFetchedResultsChangeType.Move:
            break
        case NSFetchedResultsChangeType.Update:
            break
        default:
            break
        }
    }

    override func tableView(tableView: UITableView, commitEditingStyle editingStyle: UITableViewCellEditingStyle, forRowAtIndexPath indexPath: NSIndexPath) {
        if editingStyle == .Delete {
        }

        switch editingStyle {
        case .Delete:
            managedObjectContext?.deleteObject(fetchedResultsController?.objectAtIndexPath(indexPath) as Employee)
            managedObjectContext?.save(nil)
        case .Insert:
            break
        case .None:
            break
        }

    }

    func controller(controller: NSFetchedResultsController, didChangeObject anObject: AnyObject, atIndexPath indexPath: NSIndexPath?, forChangeType type: NSFetchedResultsChangeType, newIndexPath: NSIndexPath?) {

        switch type {
        case NSFetchedResultsChangeType.Insert:
            tableView.insertRowsAtIndexPaths(NSArray(object: newIndexPath!), withRowAnimation: UITableViewRowAnimation.Fade)
            break
        case NSFetchedResultsChangeType.Delete:
            tableView.deleteRowsAtIndexPaths(NSArray(object: indexPath!), withRowAnimation: UITableViewRowAnimation.Fade)
            break
        case NSFetchedResultsChangeType.Move:
            tableView.deleteRowsAtIndexPaths(NSArray(object: indexPath!), withRowAnimation: UITableViewRowAnimation.Fade)
            tableView.insertRowsAtIndexPaths(NSArray(object: newIndexPath!), withRowAnimation: UITableViewRowAnimation.Fade)
            break
        case NSFetchedResultsChangeType.Update:
            tableView.cellForRowAtIndexPath(indexPath!)
            break
        default:
            break
        }
    }

    func controllerWillChangeContent(controller: NSFetchedResultsController) {
        tableView.beginUpdates()
    }

    func controllerDidChangeContent(controller: NSFetchedResultsController) {
        tableView.endUpdates()
    }
}

See a sample GitHub project here.