Learning Core Data Swift 5.1

A. Writing And Reading Core Data

1. Create Core data existing project, follow this step

- create a new data model

- Add a new entity and name Entity (ex: FriendEntity -> type: String )
- in right side unchecklist optional  in data model inspector




- klik entity in left side like below

2.  AppDelegate

import UIKit
import CoreData

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
    var window: UIWindow?

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        let vc = CoreDataViewController(persistenceManager: PersistenceManager.shared)
        window = UIWindow(frame: UIScreen.main.bounds)
        window?.makeKeyAndVisible()
        window?.rootViewController = UINavigationController(rootViewController: vc)

        return true
    }

}

3. Persistence Manager

import CoreData
import Foundation

final class PersistenceManager {
    private init() {}
    static let shared = PersistenceManager()
    lazy var persistentContainer: NSPersistentContainer = {
        let container = NSPersistentContainer(name: "CoreDataModule") // "CoreDataModule" is name in CoreDataModule.xcdatamodeld
        container.loadPersistentStores { _, error in
            if let error = error as NSError? {
                fatalError("Unresolve error \(error), \(error.userInfo)")
            }
        }
        return container
    }()
    
    lazy var context = persistentContainer.viewContext
    
    // MARK: Core Data Saving support
    
    func save() {
        if context.hasChanges {
            do {
                try context.save()
                print("Save succesfully")
            } catch {
                let nserror = error as NSError
                fatalError("Unresolve error \(nserror), \(nserror.userInfo)")
            }
        }
    }
    
    func fetch<T: NSManagedObject>(_ objectType: T.Type) -> [T] {
        let entityName = String(describing: objectType)
        let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: entityName)
        
        do {
            let fetchObjects = try context.fetch(fetchRequest) as? [T]
            return fetchObjects ?? [T]()
        } catch {
            print(error)
            return [T]()
        }
    }
}

4. Core Data class

import Foundation
import CoreData

@objc(FriendEntity)
public class FriendEntity: NSManagedObject {

}

5. Core Data properties

import CoreData
import Foundation

extension FriendEntity {
    @nonobjc public class func fetchRequest() -> NSFetchRequest<FriendEntity> {
        return NSFetchRequest<FriendEntity>(entityName: "FriendEntity")
    }

    @NSManaged public var name: String?
}

5. View Controller

import UIKit

class CoreDataViewController: UIViewController {
    let persistenceManager: PersistenceManager
    
    init(persistenceManager: PersistenceManager) {
        self.persistenceManager = persistenceManager
        super.init(nibName: nil, bundle: nil)
    }
    
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        createUser()
        getUsers()
    }
    
    func createUser() {
        let user = FriendEntity(context: persistenceManager.context)
        user.name = "jakki"
        
        persistenceManager.save()
    }
    
    func getUsers() {
        let users = persistenceManager.fetch(FriendEntity.self)
        users.forEach { print($0.name ?? "") }
    }
}

Thanks to KILO LOCO

link video kilo loco https://www.youtube.com/watch?v=OYRo3i9z-lM

B. Updating and Deleting in Core Data



https://www.youtube.com/watch?v=XH-osAmaU5E