Saving the right row in a TableView

Question

I`m a Beginner in swift and i have tried to build a shopping list app with a tableView in it. Nearly everthing works, except: When you reorder the rows, quit the app, and going back, the new row order was not saved. Any ideas?

This is the important part:

func tableView(_ tableView: UITableView, moveRowAt sourceIndexPath: IndexPath, to destinationIndexPath: IndexPath) {
    let movedObject = shoppingList[sourceIndexPath.row]
    shoppingList.remove(at: sourceIndexPath.row)
    shoppingList.insert(movedObject, at: destinationIndexPath.row)
}

But in will not work.....

Here is the whole code:

import UIKit
import CoreData


var shoppingList: [NSManagedObject] = [ ]


class ShoppingList_1: UIViewController, UITableViewDelegate,UITableViewDataSource {

//Anzahl Spalten -->
func numberOfSections(in tableView: UITableView) -> Int {
    return 1
}


func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
}


//**************************
//Zeilen: dynamisch; abhängig von Anzahl items in Liste -->
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return shoppingList.count
}


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


    let item = shoppingList[indexPath.row]
    let cell = Cell.dequeueReusableCell(withIdentifier: "Cell", for: indexPath)
    // <-- Prototype Cell für Ausschnitt/Sicht des Bildschirms

    cell.textLabel?.text = item.value(forKeyPath: "itemName") as? String
    cell.detailTextLabel?.text = "\(indexPath.row)"

    return cell

}

//free to use func tableView(_ tableView: UITableView, canMoveRowAt indexPath: IndexPath) -> Bool { return true }

func tableView(_ tableView: UITableView, moveRowAt sourceIndexPath: IndexPath, to destinationIndexPath: IndexPath) {  

   print("Daten geladen!\n")

    let movedObject = shoppingList[sourceIndexPath.row]
    shoppingList.remove(at: sourceIndexPath.row)
    shoppingList.insert(movedObject, at: destinationIndexPath.row)
    NSLog("%@", "\(sourceIndexPath.row) => \(destinationIndexPath.row) \(shoppingList)")
    // To check for correctness enable: self.tableView.reloadData()

}



//*****************************************************************************************************
//Durch wischen entfernen -->
func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath: IndexPath) {
    if editingStyle == .delete
    {
        guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else {return}

        let managedContext = appDelegate.persistentContainer.viewContext
        managedContext.delete(shoppingList[indexPath.row])



        do {
            try managedContext.save()

            shoppingList.remove(at: indexPath.row)
            tableView.deleteRows(at: [indexPath], with: UITableViewRowAnimation.automatic)


        } catch let err as NSError {
            print("12345", err)
        }
    }
}

@IBOutlet weak var AddButton: UIButton!
@IBOutlet weak var AddItem: UITextField!
@IBOutlet weak var Cell: UITableView!



@IBAction func EditTopRightButton(_ sender: UIBarButtonItem) {
self.Cell.isEditing = !self.Cell.isEditing
    sender.title = (self.Cell.isEditing) ? "Done" : "Edit"
}


//Button Action
@IBAction func AddButton2_Test(_ sender: Any) {
 print("My test")
 let a:Float = 2
 let b:Float = 3
 let Ergebnis:Float = a+b
 print(Ergebnis)


 if (AddItem.text !=  "")
 {
    self.save(AddItem.text!)
 }


 Cell.reloadData()


}



override func viewWillAppear(_ animated: Bool) {

    super.viewWillAppear(animated)
    guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else {return}

    let managedContext = appDelegate.persistentContainer.viewContext
    let fetchRequest = NSFetchRequest<NSManagedObject>(entityName: "Item")
    do {
        shoppingList = try managedContext.fetch(fetchRequest)
    } catch let err as NSError {
        print("Failed to fetch items", err)
    }


 }




func save(_ itemName: String){
        guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else { return }
        let managedContext = appDelegate.persistentContainer.viewContext
        let entity = NSEntityDescription.entity(forEntityName: "Item", in: managedContext)!
        let item = NSManagedObject(entity: entity, insertInto: managedContext)

        item.setValue(itemName, forKey: "itemName")

        do {
            try managedContext.save()
            shoppingList.append(item)
        } catch let err as NSError {
            print("Failed to save item",err)
        }

    }

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


    Cell.delegate = self
    Cell.dataSource = self
    AddItem.delegate = self       

}




//HINZU-->


override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

}




//*****************************************************************************************************

// extensions -->
extension ShoppingList_1 : UITextFieldDelegate {
func textFieldShouldReturn(_ textField: UITextField) -> Bool {
    AddItem.resignFirstResponder()

return true
}
}

//***************************************

Britto Thomas Britto Thomas · Accepted Answer · 2018-03-22T17:24:56

Current Working

In your code, Table view is loaded with data from Coredata at viewWillAppear. Data inserted to core data is not updated when you change the order in TableView.

So even you changed order of cell and corder in Array. Every time viewWillAppear calls Data is again fetched from Coredata with no order.

ViewWillAppear will call every time view display in screen. Incase you are coming back to this view from any other presented view ViewWillAppear will call.

Sollution

You can create a new attribute in table describing order of item in Coredata Entity & Sort the item with this order after fetching. Refer this answer to know how to set display order with core data https://stackoverflow.com/a/31907857/4845644

Or If your requirement is just to persist order to ViewController instances existence you need to change core data fetch code from viewWillAppear to viewDidLoad

override func viewDidLoad() {
    super.viewDidLoad()
    Cell.delegate = self
    Cell.dataSource = self
    AddItem.delegate = self       
    guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else {return}

    let managedContext = appDelegate.persistentContainer.viewContext
    let fetchRequest = NSFetchRequest<NSManagedObject>(entityName: "Item")
    do {
      shoppingList = try managedContext.fetch(fetchRequest)
    } catch let err as NSError {
      print("Failed to fetch items", err)
    }
}

Saving the right row in a TableView

1 Answers