CoreData-1: Insert & Fetch request from AppDelegate raywenderlich

Def -


STEP-1 Create new Project and check 'Use Core Data'

STEP-2  Go to 'app_name.xcdatamodeld' file.

STEP-3 Create entity 'Device' and two field 'name' & 'deviceType'

STEP-4 Here, Your code in AppDeletegate

=======================================================

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {

        // Override point for customization after application launch.

        

        addTestData()

        

        let context =  self.persistentContainer.viewContext

        let request = NSFetchRequest<NSFetchRequestResult>(entityName: "Device")

        request.returnsObjectsAsFaults = false

        

        do{

            let results = try context.fetch(request)

            for result in results as! [NSManagedObject]{

                if let deviceType = result.value(forKey: "deviceType") as? String, let name = result.value(forKey: "name") as? String{

                    print("Got \(deviceType) named \(name)")

                }

            }

        }catch{

            

        }

        

        return true

    }

    

    func addTestData()  {

        let context =  self.persistentContainer.viewContext

        guard let entity = NSEntityDescription.entity(forEntityName: "Device", in: context) else {

            fatalError("Could  not find entity")

        }

        

        for i in 1...25{

            let device = NSManagedObject(entity: entity, insertInto: context)

            

            device.setValue("Some Device #\(i)", forKey: "name")

            device.setValue(i%3 == 0 ? "watch" : "iphone", forKey: "deviceType")

        }

    }

=======================================================

22