无法保存 UITableViewCell 的开/关状态? [英] unable to save on/off state of a UITableViewCell?

问题描述

在名为'Item'的实体中有两个属性'time'和'isOn'(string，bool)

there are two attributes 'time' and 'isOn' (string, bool) in the entity named 'Item'

在 viewcontroller 类中，我能够为isOn"属性(在 savePressed 函数中)提供默认条件，这使得 switchbtn.isOn = true 并将其保存在该特定时间"的数据模型中

in viewcontroller class I am able to give default condition to 'isOn' attribute (in savePressed function) which makes switchbtn.isOn = true and saves it in the data model for that particular 'time'

视图控制器类:-

class ViewController: UIViewController {

    let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext

    @IBOutlet weak var timePickerView: UIDatePicker!

    @IBOutlet weak var timeLbl: UILabel!

    override func viewDidLoad() {
        super.viewDidLoad()
        timePickerView.setValue(UIColor.white, forKeyPath: "textColor")
        dateFormat()

        // Do any additional setup after loading the view.
    }

    @IBAction func savePressed(_ sender: UIBarButtonItem) {
        let entity = Item(context: context)
        entity.time = timeLbl.text
        entity.isOn = true
        saveData()
        self.dismiss(animated: true, completion: nil)
    }

    @IBAction func cancelPressed(_ sender: UIBarButtonItem) {

        self.dismiss(animated: true, completion: nil)

    }

    @IBAction func valueChanged(sender:UIDatePicker, forEvent event: UIEvent){
        dateFormat()
    }

    func saveData() {
        (UIApplication.shared.delegate as! AppDelegate).saveContext()
    }

    func dateFormat() {
        let formatter = DateFormatter()
        formatter.dateFormat = "HH:mm"
        formatter.timeStyle = .short
        timeLbl.text = formatter.string(from: timePickerView.date)
    }

}

视图控制器

在这个类中，我能够获取并显示核心数据，但不知道如何保存单元格切换按钮的状态并更新数据模型，因为没有使用didSelectRowAt"函数

in this class I am able to fetch and show the core data but don't know how to save the state of the cell switch button and update the data model as there is no use of 'didSelectRowAt' function

tableview 类:-

tableview class :-

class TableViewController: UITableViewController {

    let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext

    var items = [Item]()

    override func viewDidLoad() {
        super.viewDidLoad()
        print(arr)
    }

    override func viewWillAppear(_ animated: Bool) {
        getData()
        tableView.reloadData()
    }

    // MARK: - Table view data source

    override func numberOfSections(in tableView: UITableView) -> Int {

        return 1
    }

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

        return items.count
    }


    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "reuseIdentifier", for: indexPath) as! TableViewCell

        cell.timeLbl.text = items[indexPath.row].time
        cell.switchBtn.isOn = items[indexPath.row].isOn

        return cell
    }

    func getData() {
        let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
        do {
             items = try context.fetch(Item.fetchRequest())
        }catch{
            print("failed to get the data")
        }

    }

}

tableview

在这里，我可以打印开关的当前状态，但无法从 tableview 类访问items[indexPath.row]"

in this I am able to print the current state of the switch but cannot access the 'items[indexPath.row]' from the tableview class

单元类:-

class TableViewCell: UITableViewCell {

    @IBOutlet weak var timeLbl: UILabel!

    @IBOutlet weak var switchBtn: UISwitch!

    var alarm = Bool()

    override func awakeFromNib() {
        super.awakeFromNib()
        // Initialization code
    }

    override func setSelected(_ selected: Bool, animated: Bool) {
        super.setSelected(selected, animated: animated)

        // Configure the view for the selected state
    }

    @IBAction func valChange(_ sender: UISwitch) {
        if sender.isOn{
            switchBtn.isOn = true
        }else {
            switchBtn.isOn = false
        }
    }
}

推荐答案

在 Swift 中最有效的方法是回调闭包.

In Swift the most efficient way is a callback closure.

在单元格中添加一个属性 callback 和一个闭包传递一个 Bool 值并且没有返回值.当开关的值改变时调用回调.

In the cell add a property callback with a closure passing a Bool value and no return value. Call the callback when the value of the switch changed.

class TableViewCell: UITableViewCell {

    @IBOutlet weak var timeLbl: UILabel!
    @IBOutlet weak var switchBtn: UISwitch!

    var alarm = Bool()

    var callback : ((Bool) -> Void)?

    @IBAction func valChange(_ sender: UISwitch) {
        callback?(sender.isOn)
    }
}

在控制器的cellForRow中添加回调，在闭包中更新模型.

In cellForRow in the controller add the callback, in the closure update the model.

override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCell(withIdentifier: "reuseIdentifier", for: indexPath) as! TableViewCell

    let item = items[indexPath.row]
    cell.timeLbl.text = item.time
    cell.switchBtn.isOn = item.isOn

    cell.callback = { newValue in
        self.items[indexPath.row].isOn = newValue
    }

    return cell
}

<小时>

如果可以插入、删除或移动单元格，则还必须传递单元格以获取实际索引路径

---

If cells can be inserted, deleted or moved you have to pass also the cell to get the actual index path

class TableViewCell: UITableViewCell {

    @IBOutlet weak var timeLbl: UILabel!
    @IBOutlet weak var switchBtn: UISwitch!

    var alarm = Bool()

    var callback : ((UITableViewCell, Bool) -> Void)?

    @IBAction func valChange(_ sender: UISwitch) {
        callback?(self, sender.isOn)
    }
}

和

override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCell(withIdentifier: "reuseIdentifier", for: indexPath) as! TableViewCell

    let item = items[indexPath.row]
    cell.timeLbl.text = item.time
    cell.switchBtn.isOn = item.isOn

    cell.callback = { currentCell, newValue in
        let currentIndexPath = tableView.indexPath(for: currentCell)!
        self.items[currentIndexPath.row].isOn = newValue
    }

    return cell
}

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