How to delete row in table view core Data. Swift 3

Question

I been researching how to delete a row from a table view which the data is in Core Data. I can\'t find anything online that would help me with my code. Im really new with Co

Answer 1

You should always use "NSFetchedResultsController" whenever tableview deals with the Core Data, because "NSFetchedResultsController" is built keeping tableView in mind.

It provides features which are useful for dealing with tableView

1. Along with UITableViewDelegate & UITableviewdatasource protocols, adopt/conform to "NSFetchedResultsControllerDelegate" protocol.
2. Then implement its 3 methods to delete the record from core data. And DON'T RELOAD the tableview. NSFetchedResultsController will take care of it.

for eg. let's load the data from core data (Entity name = Movie)

var fetchedResultsController: NSFetchedResultsController

override func viewDidLoad()
{
    super.viewDidLoad()
    loadData()
}

func loadData() 
{
        fetchedResultController = getMovies(managedObjectContext: self.coreData.persistentContainer.viewContext)
        fetchedResultController.delegate = self
}


func getMovies(managedObjectContext: NSManagedObjectContext) -> NSFetchedResultsController 
{
        let fetchedResultController: NSFetchedResultsController

        let request: NSFetchRequest = Movie.fetchRequest()
        let formatSort = NSSortDescriptor(key: "format", ascending: false)
        let nameSort = NSSortDescriptor(key: "title", ascending: true)
        request.sortDescriptors = [formatSort, nameSort]

        fetchedResultController = NSFetchedResultsController(fetchRequest: request, managedObjectContext: managedObjectContext, sectionNameKeyPath: "format", cacheName: "MyMovieLibrary")

        do
        {
            try fetchedResultController.performFetch()
        }
        catch
        {
            fatalError("Error in fetching records")
        }

        return fetchedResultController
}

// MARK: - Table view data source

override func numberOfSections(in tableView: UITableView) -> Int
{
    if let sections = fetchedResultController.sections
    {
        return sections.count
    }
    return 0
}

override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int
{
    if let sections = fetchedResultController.sections
    {
        let currentSection = sections[section]
        return currentSection.numberOfObjects
    }
    return 0
}


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

    let movie = fetchedResultController.object(at: indexPath)
    cell.configureCell(movie: movie)

    return cell
}

Delete a record from core data

// Override to support editing the table view.
override func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath: IndexPath)
{
    let managedObjectContext = coreData.persistentContainer.viewContext

    if editingStyle == .delete
    {
        movieToDelete = fetchedResultController.object(at: indexPath)

        let confirmDeleteAlertController = UIAlertController(title: "Remove Movie", message: "Are you sure you would like to delete \"\(movieToDelete!.title!)\" from your movie library?", preferredStyle: UIAlertControllerStyle.actionSheet)

        let deleteAction = UIAlertAction(title: "Delete", style: UIAlertActionStyle.default, handler: { [weak self] (action: UIAlertAction) -> Void in
            managedObjectContext.delete((self?.movieToDelete!)!)
            self?.coreData.saveContext()
            self?.movieToDelete = nil
        })

        let cancelAction = UIAlertAction(title: "Cancel", style: UIAlertActionStyle.cancel, handler: { [weak self] (action: UIAlertAction) -> Void in
            self?.movieToDelete = nil
        })

        confirmDeleteAlertController.addAction(deleteAction)
        confirmDeleteAlertController.addAction(cancelAction)

        present(confirmDeleteAlertController, animated: true, completion: nil)

    }
}

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

func controller(_ controller: NSFetchedResultsController, didChange anObject: Any, at indexPath: IndexPath?, for type: NSFetchedResultsChangeType, newIndexPath: IndexPath?)
{
    switch type
    {
    case NSFetchedResultsChangeType.delete:
        print("NSFetchedResultsChangeType.Delete detected")
        if let deleteIndexPath = indexPath
        {
            tableView.deleteRows(at: [deleteIndexPath], with: UITableViewRowAnimation.fade)
        }
    case NSFetchedResultsChangeType.insert:
        print("NSFetchedResultsChangeType.Insert detected")
    case NSFetchedResultsChangeType.move:
        print("NSFetchedResultsChangeType.Move detected")
    case NSFetchedResultsChangeType.update:
        print("NSFetchedResultsChangeType.Update detected")
        tableView.reloadRows(at: [indexPath!], with: UITableViewRowAnimation.fade)
    }
}

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