我创建了一个 ToDo List 应用程序。
我使用 tableView 来列出任务。我为单元格使用自定义类。在单元格 contentView 中，我有一个标签和一个完成按钮。我已经在我的代码中成功实现了完成按钮点击操作。它工作正常。

问题

当我点击完成按钮时，它会删除最后添加的任务。但不是点击的那个。当我再次尝试单击完成按钮时，它不执行任何操作。如何解决这个错误

下面添加了GIF，点击链接

实体类 ToDo

导入基金会 导入核心数据

public class ToDo: NSManagedObject {

    public override func awakeFromInsert() {

        self.created = NSDate()
    }
}

主VC

import UIKit
import CoreData

class MainVC: UIViewController, UITableViewDelegate, UITableViewDataSource, NSFetchedResultsControllerDelegate {

    var controller: NSFetchedResultsController<ToDo>!

    @IBOutlet weak var taskTextField: CustomTextField!
    @IBOutlet weak var tableView: UITableView!

    var toDo: ToDo!

    override func viewDidLoad() {
        super.viewDidLoad()

        tableView.delegate = self
        tableView.dataSource = self

//        generateData()
        attemptFetch()

    }

    // to give view to cell
    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

        let cell = tableView.dequeueReusableCell(withIdentifier: "ItemCell", for: indexPath) as! ItemCell

        configureCell(cell: cell, indexPath: indexPath as NSIndexPath)

        return cell
    }

    // custom function
    func configureCell(cell: ItemCell, indexPath: NSIndexPath) {

        let toDo = controller.object(at: indexPath as IndexPath)

        // call the method on the ItemCell
        cell.configureCell(toDo: toDo)

        // done button click
        cell.doneBtn.tag = indexPath.row
        cell.doneBtn.addTarget(self, action: #selector(MainVC.donePressed), for: UIControlEvents.touchUpInside)


    }

    // when select a cell
    func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {

        // it ensure it have object and atleast one object in there
        if let objs = controller.fetchedObjects, objs.count > 0 {

            let task = objs[indexPath.row]

            performSegue(withIdentifier: "ItemDetailsVC", sender: task)
        }
    }

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {

        if segue.identifier == "ItemDetailsVC" {

            if let destination = segue.destination as? ItemDetailsVC {

                if let task = sender as? ToDo {

                    destination.taskDetails = task
                }
            }
        }
    }

    // count of cells
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {

        // we check here if any sections then take info of them and count
        if let sections = controller.sections {

            let sectionInfo = sections[section]

            return sectionInfo.numberOfObjects

        }

        return 0
    }

    // column count
    func numberOfSections(in tableView: UITableView) -> Int {

        if let sections = controller.sections {

            return sections.count

        }

        return 0
    }

    // give height of a cell
    func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {

        return 70
    }

    // fetching function
    func attemptFetch() {

        // create a fetch request with fetching Entity
        let fetchRequest: NSFetchRequest<ToDo> = ToDo.fetchRequest()

        // sorting area
        let dateSort = NSSortDescriptor(key: "created", ascending: true)

        fetchRequest.sortDescriptors = [dateSort]

        let controller = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: context, sectionNameKeyPath: nil, cacheName: nil)

        controller.delegate = self

        self.controller = controller

        // actual fetching
        do {

            try controller.performFetch()

        } catch {

            let error = error as NSError
            print("\(error)")
        }

    }

    // when tableView changes this function starts listen for changes and
    // it will handle that for you
    func controllerWillChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {

        tableView.beginUpdates()

    }

    func controllerDidChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {

        tableView.endUpdates()
    }

    // this function will listen for when we make change
    // insertion, deletion .. etc
    func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange anObject: Any, at indexPath: IndexPath?, for type: NSFetchedResultsChangeType, newIndexPath: IndexPath?) {

        switch type {
        case.insert:
            if let indexPath = newIndexPath {
                tableView.insertRows(at: [indexPath], with: .fade)
            }

            break

        case.delete:
            if let indexPath = indexPath {
                tableView.deleteRows(at: [indexPath], with: .fade)


            }

            break

        case.update:
            if let indexPath = indexPath {

                let cell = tableView.cellForRow(at: indexPath)
                //update the cell data

                configureCell(cell: cell as! ItemCell, indexPath: indexPath as NSIndexPath)
            }

            break

        case.move:
            if let indexPath = indexPath {
                tableView.deleteRows(at: [indexPath], with: .fade)
            }

            if let indexPath = newIndexPath {
                tableView.insertRows(at: [indexPath], with: .fade)
            }

            break
    }
}

    @IBAction func addBtnPressed(_ sender: UIButton) {

        if taskTextField.text != "" && taskTextField.text != nil {

        toDo = ToDo(context: context)

        if let task = taskTextField.text {

            toDo.title = task
        }

        ad.saveContext()

        taskTextField.text = ""

        self.tableView.reloadData()

        }

    }

    // done button
    func donePressed() {



        if toDo != nil {

        context.delete(toDo)
        ad.saveContext()

        }


    }



    func generateData() {

        let task = ToDo(context: context)
        task.title = "alwin"

        let task1 = ToDo(context: context)
        task1.title = "rambo"

        let task2 = ToDo(context: context)
        task2.title = "monisha"

        let task3 = ToDo(context: context)
        task3.title = "wounderlist"

        let task4 = ToDo(context: context)
        task4.title = "presentation"

        let task5 = ToDo(context: context)
        task5.title = "roundup"

        // to save data
        ad.saveContext()
    }

}

ItemDetailsVC

import UIKit

class ItemDetailsVC: UIViewController {

    var taskDetails: ToDo?

    @IBOutlet weak var detailsLbl: UILabel!

    override func viewDidLoad() {
        super.viewDidLoad()

        // to clear the <DreamLIst to < only
        if let topItem = self.navigationController?.navigationBar.topItem {
            topItem.backBarButtonItem = UIBarButtonItem(title: "", style: UIBarButtonItemStyle.plain, target: nil, action: nil)

            // this is execute when tap on an existing cell
            if taskDetails != nil {

                loadItemData()
            }
        }

    }

    func loadItemData() {

        if let task = taskDetails {

            detailsLbl.text = task.title
        }

    }

    override func viewDidLayoutSubviews() {

        detailsLbl.sizeToFit()
    }


    @IBAction func deletePressed(_ sender: UIBarButtonItem) {

        if taskDetails != nil {

            context.delete(taskDetails!)
            ad.saveContext()
        }

        _ = navigationController?.popViewController(animated: true)

    }

}

Storyboard，点击下面的链接

项目单元格

import UIKit

class ItemCell: UITableViewCell {


    @IBOutlet weak var taskTitle: UILabel!

    @IBOutlet weak var doneBtn: UIButton!

    var toDo: ToDo?

    func configureCell(toDo: ToDo) {

    taskTitle.text = toDo.title

    }

}

最佳答案

好的，目前您正在将完成按钮的选择器设置到其容器(单元格)之外，这通常是一种不好的做法，您正在使用 ToDo 配置单元格，但没有在单元格内部分配可选项，据说可以保留对 ToDo 的引用。

在我看来，我会稍微改变一下，以便您首先存储对 ToDo 的引用:

func configureCell(toDo: ToDo) {
   self.toDo = toDo
taskTitle.text = toDo.title

}

现在在您的单元格上创建一个协议(protocol)，然后为单元格配置一个 ToDo 和一个代表，然后在按下按钮时告诉代表您的按钮被按下了相关的 ToDo...

protocol ToDoCellDelegate: class {
  func toDoCellButtonPressed(todo: ToDo?)
}

现在在你的手机上配置为:

func configureCell(toDo: ToDo, delegate: ToDoCellDelegate) {
self.delegate = delegate
self.toDo = toDo

taskTitle.text = toDo.title

}

并在单元格中添加对委托(delegate)的引用:

weak var delegate: ToDoCellDelegate?

现在将您的按钮选择器更改为单元格内的函数

func buttonPressed() {
    self.delegate?.cellToDoButtonPressed(toDo: toDo)
}

然后在您的 VC 中，您符合在配置中传递 self 的委托(delegate)并实现委托(delegate):

extension ItemDetailsVC: ToDoCellDelegate {
    func toDoCellButtonPress(toDo: ToDo?) {
         if let t = toDo {
            //tell context to delete todo and remove cell.
         }
    }
}

关于ios - 如何通过单击单元格中的按钮来删除 tableView 中的单元格？使用核心数据，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/41743391/