Question

我是swift的初学者，我试图建立一个带有tableView的购物清单应用程序。近乎工作，除了：重新排序行，退出应用程序并返回时，新行顺序未保存。有什么想法吗？

这是重要的部分：

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)
}

但是不会起作用.....

以下是整个代码：

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

}

//免费使用 func tableView（_ tableView：UITableView，canMoveRowAt indexPath：IndexPath） - ＆gt;布尔{ 返回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
}
}

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

Answer 1

当前工作

在您的代码中，Table视图加载了来自viewWillAppear的Coredata的数据。在TableView中更改顺序时，不会更新插入到核心数据的数据。

所以即使你改变了Array中单元格和corder的顺序。每次viewWillAppear调用时，都会从没有订单的Coredata中再次获取数据。

每次在屏幕中显示视图时，

ViewWillAppear都会调用。如果您从任何其他呈现的视图ViewWillAppear将回拨此视图。

<强> Sollution

您可以在表格中创建一个新属性，描述Coredata Entity＆amp;在获取后按此顺序对项目进行排序。请参阅此答案以了解如何使用核心数据设置显示顺序 https://stackoverflow.com/a/31907857/4845644

或者如果您的要求只是为了保持订单到ViewController实例，则需要将核心数据提取代码从viewWillAppear更改为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)
    }
}

在TableView中保存右侧行

1 个答案: