How to delete a row from UITableView swift 4 wherein data is stored using CoreData?

Question

I am a beginner trying to learn the basic concepts of iOS and swift. So, I am making a demo app wherein I store names of people using UITableView. For making the app storage persistent I used core data with only one entity named 'Person' with a single attribute as 'name' which is a string value. To level up this application I need to add delete functionality. As we see in lot of iOS apps, the delete feature on swiping left, I want to implement the same functionality in this app. I have looked up on various solutions but I can't really get a hold of how I'll be able to delete a row and update the table in core data at the same time. I have been stuck at this problem since hours trying to delete a row in UITableView using swipe gesture. Any help would be appreciated.

Below is my code:

ViewController.swift

import UIKit
import CoreData

class ViewController: UIViewController {

    @IBOutlet weak var tableView: UITableView!

    var people: [NSManagedObject] = []

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        title = "The List"
        tableView.register(UITableViewCell.self,
                           forCellReuseIdentifier: "Cell")
    }

    // Implement the addName IBAction
    @IBAction func addName(_ sender: UIBarButtonItem) {
        let alert = UIAlertController(title: "New Name", message: "Add a new name", preferredStyle: .alert)
        let saveAction = UIAlertAction (title: "Save", style: .default) {
            [unowned self] action in
            guard let textField = alert.textFields?.first, let nameToSave = textField.text else {
                return
            }
            self.save(name: nameToSave)
            self.tableView.reloadData()
        }
        let cancelAction = UIAlertAction(title: "Cancel", style: .cancel)
        alert.addTextField()

        alert.addAction(saveAction)
        alert.addAction(cancelAction)

        present(alert, animated: true)
    }

    // MARK: - SAVING TO CORE DATA

    // CoreData kicks in here!
    func save(name: String) {
        guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else {
            return
        }
        // 1
        let managedContext = appDelegate.persistentContainer.viewContext

        // 2
        let entity = NSEntityDescription.entity(forEntityName: "Person", in: managedContext)!
        let person = NSManagedObject(entity: entity, insertInto: managedContext)

        // 3
        person.setValue(name, forKeyPath: "name")

        // 4
        do {
            try managedContext.save()
            people.append(person)
        } catch let error as NSError {
            print("Could not save. \(error), \(error.userInfo)")
        }
    }

    // MARK: - FETCHING FROM CORE DATA

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)

        // 1
        guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else {
            return
        }

        let managedContext = appDelegate.persistentContainer.viewContext

        // 2
        let fetchRequest = NSFetchRequest<NSManagedObject>(entityName: "Person")

        // 3
        do {
            people = try
                managedContext.fetch(fetchRequest)
        } catch let error as NSError {
            print("Could not save. \(error), \(error.userInfo)")
        }
    }
}
// MARK: - UITableViewDataSource

extension ViewController: UITableViewDataSource {

    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return people.count
    }

    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let person = people[indexPath.row]
        let cell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath)
        cell.textLabel?.text = person.value(forKeyPath: "name") as? String
        return cell
    }
}

// MARK: - UITableViewDelegate

extension ViewController: UITableViewDelegate {
    func tableView(_ tableView: UITableView, canEditRowAt indexPath: IndexPath) -> Bool {
        return true
    }

    func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCell.EditingStyle, forRowAt indexPath: IndexPath) {
        if (editingStyle == .delete) {
            // handle delete (by removing the data from your array and updating the tableview)

        }
    }
}

App Screen:

Data model:

Answer 1

You have to delete the managed object by calling delete(_:) on the managed object context, e.g.:

guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else {
    return
}
let managedContext = appDelegate.persistentContainer.viewContext
let person = people[indexPath.row]
managedContext.delete(person)

And to commit the change, call save() on the managed object context:

try? managedContext.save()

Then, don't forget to also update the person cache in your view controller:

people.remove(at: indexPath.row)

And finally, delete the row in your table view:

tableView.deleteRows(at: [indexPath], with: .automatic)

This should accomplish what you want.

The missing implementation could therefor be:

 func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCell.EditingStyle, forRowAt indexPath: IndexPath) {
    if editingStyle == .delete {

        // delete the person in core data
        guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else {
            return
        }
        let managedContext = appDelegate.persistentContainer.viewContext
        let person = people[indexPath.row]
        managedContext.delete(person)
        try? managedContext.save()

        // remove the person from cache
        people.remove(at: indexPath.row)

        // delete row from table view
        tableView.deleteRows(at: [indexPath], with: .automatic)
    }
}