swift - CoreData

Question

I have a custom NSManagedObject:

import Foundation
import CoreData
@objc(Article)

class Article: NSManagedObject {

    @NSManaged var articleID: String
    @NSManaged var isFavorite: Bool
    init(entity: NSEntityDescription, insertIntoManagedObjectContext context: NSManagedObjectContext?, articleID: String, isFavorite: Bool) {
        super.init(entity: entity, insertIntoManagedObjectContext: context)
        self.articleID = articleID
        self.isFavorite = isFavorite
    }

    override init(entity: NSEntityDescription, insertIntoManagedObjectContext context: NSManagedObjectContext?) {
        super.init(entity: entity, insertIntoManagedObjectContext: context)
    }
}

But I got error when I trie to add a new entry to CoreData:

let articleEntity = NSEntityDescription.entityForName("Article", inManagedObjectContext: self.context!)
let newArticle = Article(entity: articleEntity!, insertIntoManagedObjectContext: self.context!)
newArticle.articleID = articleID
newArticle.isFavorite = true

Use of unresolved identifier 'Article'

Answer 1

From the information above, it looks like you have't added the class for the entity in configuration of the coredata. Make sure you have mapped class against entity in the configuration of .xcdatamodeld file. You can check the below example.

Answer 2

// 1) Swift File

import Foundation import CoreData import UIKit

class DatabaseHelper{

static var shareInstance = DatabaseHelper()
let context = (UIApplication.shared.delegate as? AppDelegate)?.persistentContainer.viewContext

func save(object:[String:String]){
    let student = NSEntityDescription.insertNewObject(forEntityName: "Student", into: context!) as! Student

    student.name = object["name"]
    student.address = object["address"]
    student.city = object["city"]
    student.mobile  = object["mobile"]

    do{

        try context?.save()
    }catch{

        print("Data is not save")
    }
}

func getStudentData() -> [Student]{

    var student = [Student]()
    let fatchRequest = NSFetchRequest<NSManagedObject>(entityName: "Student")

    do{
        student = try context?.fetch(fatchRequest)as![Student]
    }catch{

        print("can not get Data")
    }
    return student
}

// 2) view Controller

import UIKit

class ViewController: UIViewController {

@IBOutlet weak var txtCity: UITextField!
@IBOutlet weak var txtMobile: UITextField!
@IBOutlet weak var txtAddress: UITextField!
@IBOutlet weak var txtName: UITextField!

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.
}

@IBAction func btnSaveData(_ sender: Any) {

    var dict = ["name":txtName.text,"address":txtAddress.text,"city":txtCity.text,"mobile":txtMobile.text]
    DatabaseHelper.shareInstance.save(object: dict as! [String : String])

}
@IBAction func btnShowAction(_ sender: Any) {

    let show = storyboard?.instantiateViewController(withIdentifier: "AnotherViewController")as! AnotherViewController

    self.navigationController?.pushViewController(show, animated: true)
}

}

// 3) Data get in table View

import UIKit

class AnotherViewController: UIViewController,UITableViewDelegate,UITableViewDataSource{

@IBOutlet weak var tblView: UITableView!

var student = [Student]()

override func viewDidLoad() {
    super.viewDidLoad()

    student = DatabaseHelper.shareInstance.getStudentData()
}

func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {

    return student.count
}

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

    let cell = tblView.dequeueReusableCell(withIdentifier: "tblCell", for: indexPath)as! tblCell
    cell.lblName.text = student[indexPath.row].name
    cell.lblAddress.text = student[indexPath.row].address
    cell.lblCity.text = student[indexPath.row].city
    cell.lblMobile.text = student[indexPath.row].mobile
    return cell
}

} class tblCell : UITableViewCell{

@IBOutlet weak var lblName: UILabel!
@IBOutlet weak var lblAddress: UILabel!
@IBOutlet weak var lblCity: UILabel!
@IBOutlet weak var lblMobile: UILabel!

}

Answer 3

// 4) AppViewController

class AppDelegate: UIResponder, UIApplicationDelegate {

var window: UIWindow?


func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
    print("Document Directory:", FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).last ?? "Not found!!")
    return true
}