ios - 如何使用委托(delegate)和协议(protocol)快速编辑和传回单元格数据

Question

我有两个 VC，第一个是 tableView，第二个是 detailedView VC，您可以在其中向 tableView 添加新项目。我已经实现了使用 segues 向前传递数据(从第一个 VC 中的加号按钮)，并在向 tableView 添加新项目时使用委托(delegate)和协议(protocol)向后传递数据(在第二个 VC 上点击保存按钮时触发)。

我从原型(prototype)单元添加了一个 segue 到第二个 VC(详细 View )，我还设法在第一个 VC 中测试了哪个 segue 被触发，即:添加新项目或转到该项目的 detailedView。我面临的问题是，第二个 VC 中的保存按钮不再起作用(取消按钮也不起作用)，我希望能够在第二个 VC 中编辑文本字段并点击保存按钮将编辑的项目保存回来在第一个。我找到了一种使用 unwind segues 来实现它的方法，但是我想知道如何使用 delegate 来实现它？

我的第一个 VC 代码:

class ThingsTableViewController: UITableViewController, CanReceive {

    var myThings = [Thing]()

    override func viewDidLoad() {
        super.viewDidLoad()

    }

    // MARK: - Table view data source

    override func numberOfSections(in tableView: UITableView) -> Int {
        return 1
    }

    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return myThings.count
    }

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

        cell.textLabel?.text = myThings[indexPath.row].name
        cell.detailTextLabel?.text = myThings[indexPath.row].type

        return cell
    }

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

        if segue.identifier == "addNewThing" {

            let secondVC = segue.destination as! UINavigationController

            let ThingsViewController = secondVC.topViewController as! ThingsViewController

            ThingsViewController.delegate = self

        } else if segue.identifier == "showDetail" {

            guard let thingDetailViewController = segue.destination as? ThingsViewController else {fatalError("Unknown Destination")}

            guard let selectedCell = sender as? UITableViewCell else {
                fatalError("Unexpected sender: \(sender)")
            }

            guard let indexPath = tableView.indexPath(for: selectedCell) else {
                fatalError("The selected cell is not being displayed by the table")
            }

            let selectedThing = myThings[indexPath.row]
            thingDetailViewController.thing = selectedThing

        }
    }

    func dataReceived(data: Thing) {

        if let selectedIndexPath = tableView.indexPathForSelectedRow {

        myThings[selectedIndexPath.row] = data
        tableView.reloadRows(at: [selectedIndexPath], with: .none)

        } else {

        myThings.append(data)
        tableView.reloadData()



    }

}

第二个 vc 中的代码如下:

 protocol CanReceive {

func dataReceived(data: Thing)

    }

}

class ThingsViewController: UIViewController, UITextFieldDelegate {

    var delegate : CanReceive?
    var thing : Thing?

    @IBOutlet weak var thingNameTextField: UITextField!

    @IBOutlet weak var thingTypeTextfield: UITextField!

    @IBAction func saveThingButton(_ sender: UIBarButtonItem) {
        let newThing = Thing(name: thingNameTextField.text!, type: thingTypeTextfield.text!)

        delegate?.dataReceived(data: newThing)

        self.dismiss(animated: true, completion: nil)
        self.navigationController?.popViewController(animated: true)

    }

    @IBAction func cancelButton(_ sender: UIBarButtonItem) {
        self.dismiss(animated: true, completion: nil)
        self.navigationController?.popViewController(animated: true) 
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        thingNameTextField.delegate = self

        updateSaveButtonState()

        if let thing = thing {
            navigationItem.title = thing.name
            thingNameTextField.text = thing.name
            thingTypeTextfield.text = thing.type

        }
    }

    // MARK: UITextField Delegate

    // get triggered when the user hit the return key on the keyboard
    func textFieldShouldReturn(_ textField: UITextField) -> Bool {
        thingNameTextField.resignFirstResponder()
        self.navigationItem.rightBarButtonItem?.isEnabled = true
        return true
    }

    //gives chance to read info in text field and do something with it
    func textFieldDidEndEditing(_ textField: UITextField) {
        updateSaveButtonState()
        navigationItem.title = thingNameTextField.text
    }

    func updateSaveButtonState() {

        let text = thingNameTextField.text
        self.navigationItem.rightBarButtonItem?.isEnabled = !text!.isEmpty
    }

}

Answer 1

您正在为 segue 的标识符为 addNewThing 的情况设置 delegate，但是标识符为 showDetail 的情况呢？

如果segue的标识符是showDetail，则设置segue目的地的delegate

if segue.identifier == "addNewThing" {
    ...
} else if segue.identifier == "showDetail" {
    ...
    thingDetailViewController.delegate = self
    ...
}

---

然后当你需要关闭导航 Controller 中嵌入的 ViewController 时，只需关闭它然后关闭导航 Controller