ios - 如何保留 TableView 行？

Question

我正在创建一个ios应用程序，它将每天向我显示一组特定于用户的任务，我单击删除以显示其完成情况。我将任务保存在核心数据中，然后单击即可删除表格 View 行。我不会删除 coredata 中用户定义的数据，并且需要每天重新加载。如果应用程序在新的一天打开，我使用 newDay() 函数来决定从 coredata 加载数据。我应该怎么做才能记住当天已完成的所有任务？我是否需要创建另一个实体来记住所有任务已完成，或者是否有更简单的方法？

var tasks: [NSManagedObject] = []
let defaults = UserDefaults.standard
var calender = Calendar.current

override func viewDidLoad() {
    super.viewDidLoad()

    title = "DailyTasker"
    navigationItem.leftBarButtonItem = editButtonItem

}

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)

    let checkDate = newDay()
    if checkDate{

    //1
    guard let appDelegate =
        UIApplication.shared.delegate as? AppDelegate else {
            return
    }

    let managedContext =
        appDelegate.persistentContainer.viewContext

    //2
    let fetchRequest =
        NSFetchRequest<NSManagedObject>(entityName: "Task")

    //3
    do {
        tasks = try managedContext.fetch(fetchRequest)
        defaults.set(Date(), forKey: "LastRun")
    } catch let error as NSError {
        print("Could not fetch. \(error), \(error.userInfo)")
    }
    }
}

func newDay() -> Bool{
    if let lastRun = defaults.object(forKey: "LastRun") as? Date{
        if !calender.isDateInToday(lastRun){
            return true
        } else {
            return false
        }
    } else {
        return true
    }

}


@IBAction func addName(_ sender: UIBarButtonItem) {
    let alert = UIAlertController(title: "New Task",
                                  message: "Add a new task",
                                  preferredStyle: .alert)

    let saveAction = UIAlertAction(title: "Save",
                                   style: .default) {
                                    [unowned self] action in

                                    guard let textField = alert.textFields?.first,
                                        let nameToSave = textField.text else {
                                            return
                                    }

                                    self.save(name: nameToSave)
                                    self.tableView.reloadData()
    }

    let cancelAction = UIAlertAction(title: "Cancel",
                                     style: .default)

    alert.addTextField()

    alert.addAction(saveAction)
    alert.addAction(cancelAction)

    present(alert, animated: true)
}

func save(name: String) {

    guard let appDelegate =
        UIApplication.shared.delegate as? AppDelegate else {
            return
    }

    // 1
    let managedContext =
        appDelegate.persistentContainer.viewContext

    // 2
    let entity =
        NSEntityDescription.entity(forEntityName: "Task",
                                   in: managedContext)!

    let task = NSManagedObject(entity: entity,
                               insertInto: managedContext)

    // 3
    task.setValue(name, forKeyPath: "name")

    // 4
    do {
        try managedContext.save()
        tasks.append(task)
    } catch let error as NSError {
        print("Could not save. \(error), \(error.userInfo)")
    }

}

// MARK: - Table view data source

override func numberOfSections(in tableView: UITableView) -> Int {
    // #warning Incomplete implementation, return the number of sections
    return 1
}

override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    // #warning Incomplete implementation, return the number of rows
    return tasks.count
}


override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let task = tasks[indexPath.row]
    let cell = tableView.dequeueReusableCell(withIdentifier: "TaskerCell", for: indexPath)
    cell.textLabel?.text = task.value(forKeyPath: "name") as? String

    return cell
}       

 // Override to support editing the table view.
 override func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath: IndexPath) {
 if editingStyle == .delete {
 // Delete the row from the data source
 tasks.remove(at: indexPath.row)
 tableView.deleteRows(at: [indexPath], with: .fade)
 } else if editingStyle == .insert {

 }
 }

 override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
    tasks.remove(at: indexPath.row)
    tableView.deleteRows(at: [indexPath], with: .fade)
}    

}

Answer 1

您可以向任务添加日期属性，并将其命名为 lastDone。然后，您可以在任务完成时将其设置为当前日期时间，并在获取任务实例时使用谓词，这样您就只能获取今天未完成的任务。

 task.lastDone = Date()

我不确定你如何定义“今天”，但是this question应该帮助您创建一个谓词来正确过滤您的任务，尽管您可能还希望包含 lastDone 为 null 的任务。