CoreData, displaying saved journeys in a tableview

Question

I am trying to display a list of all journeys recorded in a fitness-style app in a table view to show the distance (boolean) and date (timestamp) of each journey.

At the moment I have just created a variable to contain the Journeys from the core data file. When I print out the journeysArray, it shows 0 in the console even though there are some recorded journeys.

import UIKit
import CoreData

class SavedJourneysViewController: UITableViewController {

    var journeyArray: [Journey] = []

    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view.
    }

    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        print(journeyArray.count)
        return journeyArray.count

    }

    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "JourneyItem", for: indexPath)
        return cell

    }

Answer 1

If Journey is your NSManagedObject subclass, you should use a NSFetchedResultsController to fetch the persisted objects.

Your SavedJourneysViewController must have a reference to the NSManagedObjectContext instance that you'll use to fetch your Journey objects. Let's assume that you have a viewContext property of type NSManagedObjectContext in your SavedJourneysViewController that's being set from the outside, wherever you initialize your SavedJourneysViewController .

You'll want to declare a fetchedResultsController in SavedJourneysViewController .

private lazy var fetchedResultsController: NSFetchedResultsController<Journey> = {
    let fetchRequest: NSFetchRequest< Journey > = Journey.fetchRequest()
    let sortDescriptor = NSSortDescriptor(keyPath: \Journey.date, ascending: true)
    fetchRequest.sortDescriptors = [sortDescriptor]
    let fetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: viewContext, sectionNameKeyPath: nil, cacheName: nil)
    return fetchedResultsController
}()

Then perform fetch in viewDidLoad (for example) by calling try? fetchedResultsController.performFetch() try? fetchedResultsController.performFetch() :

Then in numberOfRowsInSection return fetchedResultsController.sections?[section].objects?.count ?? 0 fetchedResultsController.sections?[section].objects?.count ?? 0 :

func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return fetchedResultsController.sections?[section].objects?.count ?? 0
}

Don't forget about implementing func numberOfSections(in tableView: UITableView) -> Int and returning fetchedResultsController.sections?.count ?? 0 fetchedResultsController.sections?.count ?? 0 :

func numberOfSections(in tableView: UITableView) -> Int {
    return fetchedResultsController.sections?.count ?? 0
}

In cellForRowAt , configure your cell with a Journey object:

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = let cell = tableView.dequeueReusableCell(withIdentifier: "JourneyItem", for: indexPath)
    guard let journey = fetchedResultsController.sections?[indexPath.section].objects?[indexPath.row] as? Journey else {
        return cell
    }
    // handle cell configuration
    cell.textLabel?.text = String(journey.distance)
    return cell
}

More about using NSFetchedResultsController with UITableViewController -

• https://cocoacasts.com/populate-a-table-view-with-nsfetchedresultscontroller-and-swift-3
• https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/CoreData/nsfetchedresultscontroller.html