[swift] Add / Delete Tasks with CoreData

for Add / Delete Tasks with CoreData, Refer below code

with Closure, Run Reload Table or fetch CoreData, Once Save/Delete method has been completed

Add CoreData after creating xcode Project without CoreData

 

Create CoreData

Create Data Model File

Create new file with “New File” (CoreData -> Data Model)

Data Model file name is “HitList”, then file named “HitList.xcdatamodeld” in xcode Project

 

Create Entity & Attribute

in this case, Create Entity (DB table in SQL) named “Person” and Attribute (Column in SQL) named “Name” within “Person” Entity

with “Add Entity”, Create “Person” Entity

with “Add Attribute”, Create “Name” Attribute

 

 

AppDelegate.swift

Add below code into AppDelegate.swift

• when create project with CoreData, these code will be generate automatically

Should add Data Model name into on “NSPersistentContainer”

// MARK: - Core Data stack

  lazy var persistentContainer: NSPersistentContainer = {
    /*
     The persistent container for the application. This implementation
     creates and returns a container, having loaded the store for the
     application to it. This property is optional since there are legitimate
     error conditions that could cause the creation of the store to fail.
     */
    let container = NSPersistentContainer(name: "HitList")
    container.loadPersistentStores(completionHandler: { (storeDescription, error) in
      if let error = error as NSError? {
        // Replace this implementation with code to handle the error appropriately.
        // fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.

        /*
         Typical reasons for an error here include:
         * The parent directory does not exist, cannot be created, or disallows writing.
         * The persistent store is not accessible, due to permissions or data protection when the device is locked.
         * The device is out of space.
         * The store could not be migrated to the current model version.
         Check the error message to determine what the actual problem was.
         */
        fatalError("Unresolved error \(error), \(error.userInfo)")
      }
    })
    return container
  }()

  // MARK: - Core Data Saving support

  func saveContext () {
    let context = persistentContainer.viewContext
    if context.hasChanges {
      do {
        try context.save()
      } catch {
        // Replace this implementation with code to handle the error appropriately.
        // fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
        let nserror = error as NSError
        fatalError("Unresolved error \(nserror), \(nserror.userInfo)")
      }
    }
  }  

ViewController.swift

Install TableView on ViewController

with fetchPersonData, retrieve NSManagedObject from CoreDate, then add NSManagedObject into Array named “people”

NSManagedObject is “Dictionary” type. You can access each element with below code

cell.textLabel?.text = person.value(forKeyPath: “name”) as? String

import UIKit
import CoreData

class ViewController: UIViewController {

  @IBOutlet weak var tableView: UITableView!
  var people: [NSManagedObject] = []

  override func viewDidLoad() {
    super.viewDidLoad()

    title = "The List"
    tableView.register(UITableViewCell.self,
                       forCellReuseIdentifier: "Cell")
  }

  override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)
    
    fetchPersonData(){
      self.tableView.reloadData()
    }
  }

  @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.saveName(name: nameToSave){
        self.fetchPersonData() {
          self.tableView.reloadData()
        }
      }
    }

    let cancelAction = UIAlertAction(title: "Cancel",
                                     style: .default)

    alert.addTextField()

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

    present(alert, animated: true)
  }

  func save(name: String) {
    guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else {
      return
    }

    let managedContext = appDelegate.persistentContainer.viewContext

    let entity = NSEntityDescription.entity(forEntityName: "Person",
                                            in: managedContext)!

    let person = NSManagedObject(entity: entity,
                                 insertInto: managedContext)

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

    do {
      try managedContext.save()
      people.append(person)
    } 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
  }
  
  
  func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath: IndexPath) {
    if editingStyle == .delete {
      let person = people[indexPath.row]

      deleteName(managedObject: person){
        self.fetchPersonData(){
          self.tableView.deleteRows(at: [indexPath], with: .fade)
          self.tableView.reloadData()
        }
      }

    }
  }
  
}


//MARK: Controll CoreData

extension ViewController {
  func saveName(name: String, completion: (()->Void)?) {
    
    guard let appDelegate =
      UIApplication.shared.delegate as? AppDelegate else {
        return
    }
    
    let managedContext =
      appDelegate.persistentContainer.viewContext
    
    let entity =
      NSEntityDescription.entity(forEntityName: "Person",
                                 in: managedContext)!
    
    let person = NSManagedObject(entity: entity,
                                 insertInto: managedContext)
    
    person.setValue(name, forKeyPath: "name")
    
    do {
      try managedContext.save()
      completion?()
    } catch let error as NSError {
      print("Could not save. \(error), \(error.userInfo)")
    }
  }
  
  func fetchPersonData(completion: (()->Void)?) {
    
    guard let appDelegate =
      UIApplication.shared.delegate as? AppDelegate else {
        return
    }
    
    let managedContext =
      appDelegate.persistentContainer.viewContext
    
    let fetchRequest =
      NSFetchRequest(entityName: "Person")
    
    do {
      people = try managedContext.fetch(fetchRequest)
      completion?()
    } catch let error as NSError {
      print("Could not fetch. \(error), \(error.userInfo)")
    }
  }
  
  func updateName(managedObject: NSManagedObject, newName: String, completion: (()->Void)?) {
    
    guard let appDelegate =
      UIApplication.shared.delegate as? AppDelegate else {
        return
    }
    
    let managedContext =
      appDelegate.persistentContainer.viewContext
    
    do {
      managedObject.setValue(newName, forKey: "name")
      
      try managedContext.save()
      completion?()
    } catch {
      
    }
  }
  func deleteName(managedObject: NSManagedObject, completion: (()->Void)?) {
    
    guard let appDelegate =
      UIApplication.shared.delegate as? AppDelegate else {
        return
    }
    
    let managedContext =
      appDelegate.persistentContainer.viewContext
    
    do {
      managedContext.delete(managedObject)
      print("deleteName")
      try managedContext.save()
      completion?()
    } catch {
      print("deleteName error")
    }
  }
}