通过导航返回按钮传递数据

Question

我处于这种情况：

我使用prepare for segue将4个数组从进度表传递到详细练习，它工作正常！当我尝试将数据从详细练习控制器传递回进度表控制器时，问题就开始了。我想使用默认的导航返回按钮返回父视图。实际上我正在使用此代码但它不起作用，数据从子视图传递到父视图但我在进度表中看不到结果，似乎我需要刷新但我也尝试了 reloadData在 viewDidLoad 之后它不起作用。有什么建议吗？谢谢。

override func viewWillDisappear(animated : Bool) {
    super.viewWillDisappear(animated)

    if (self.isMovingFromParentViewController()){
        print("n'drio")

        let historyView = self.storyboard!.instantiateViewControllerWithIdentifier("historyView") as! HistoryTableViewController
        historyView.isFirstTime = false
        historyView.arrayData = arrayDataDetails
        historyView.arrayRipetizioni = arrayRipetizioniDetails
        historyView.arrayPeso = arrayPesoDetails
        historyView.arrayRecupero = arrayRecuperoDetails
        historyView.tableView.reloadData()
    }
}

Answer 1

当您按下返回按钮时，导航控制器将调用navigationController(willShowViewController:)，因此您可以使用它将数据传回初始视图控制器。示例如下：

使用UINavigationControllerDelegate：

class DetailsViewController: UIViewController, UINavigationControllerDelegate {
                                                        //     ^
    var data: [String] = []                             // Important!

    override func viewDidLoad() {
        super.viewDidLoad()

        navigationController?.delegate = self

        data = ["data has changed!"]
    }
}

斯威夫特 2：

extension DetailsViewController: UINavigationControllerDelegate {
    func navigationController(navigationController: UINavigationController, willShowViewController viewController: UIViewController, animated: Bool) {
        if let controller = viewController as? ProgressTableViewController {
            controller.data = data    // Here you pass the data back to your original view controller
        }
    }
}

斯威夫特 3：

extension DetailsViewController: UINavigationControllerDelegate {
    func navigationController(_ navigationController: UINavigationController, willShow viewController: UIViewController, animated: Bool) {
        (viewController as? ProgressTableViewController)?.data = data // Here you pass the to your original view controller
    }
}

在本例中，关键是使用UINavigationControllerDelegate 并设置导航控制器的委托（在本例中为self）。完成此操作后，您可以使用返回按钮将数据发送回初始视图控制器。

我个人更喜欢为我的数据使用一个类：

为您的数据使用自定义类：

class Data {
    var array: [String] = []
}

进度视图控制器：

class ProgressTableViewController: UITableViewController {

    var data = Data()

    override func viewDidLoad() {
        super.viewDidLoad()

        data.array = ["some data"]
    }

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

        tableView.reloadData()
    }

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

    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = UITableViewCell()

        cell.textLabel?.text = data.array[indexPath.row]

        return cell
    }

    override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        performSegue(withIdentifier: "exerciseSegue", sender: self)
    }

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        if segue.identifier == "exerciseSegue" {
            let destination = segue.destinationViewController as! DetailsViewController
            destination.data = data
        }
    }
}

详情视图控制器：

class DetailsViewController: UIViewController {

    var data = Data()

    override func viewDidLoad() {
        super.viewDidLoad()

        data.array = ["data has changed!"]
    }
}

在最后一个示例中，您不必担心传递数据。每当您更改数据时，使用相同类的控制器也会发生更改。

Answer 2

通常，协议和委托用于在屏幕之间来回传递数据。

// Define a delegate that is known to both view controllers
protocol DetailsExerciseDelegate {
    func detailsWillDisappear(...);
}

class DetailsExerciseViewController {
    // Accept the delegate as a property on the details view controller
    var delegate : DetailsExerciseDelegate

    override func viewWillDisappear(animated : Bool) {
        super.viewWillDisappear(animated)

        // When you want to send data back to the caller
        // call the method on the delegate
        if let delegate = self.delegate {
            delegate.detailsWillDisappear(/* your data in one or more parameters */)
        }
    }
}

// Implement the delegate by adding the required function
class ProgressTableViewController: DetailsExerciseDelegate {
    ...

    func detailsWillDisappear(...) {
        // When the child calls the function, update the screen
        historyView.isFirstTime = false
        historyView.arrayData = arrayDataDetails
        historyView.arrayRipetizioni = arrayRipetizioniDetails
        historyView.arrayPeso = arrayPesoDetails
        historyView.arrayRecupero = arrayRecuperoDetails
        historyView.tableView.reloadData()
    }

    override func prepareForSegue(segue: UIStoryboardSegue?, sender: AnyObject?) {
        if segue!.identifier == "DetailsExcercise" {
            // And finally, when launching the child view,
            // make sure to set the delegate.
            let viewController = segue!.destinationViewController as DetailsExerciseViewController
            viewController.delegate = self
        }
    }
}

话虽如此，单击后退按钮时尝试保存数据似乎是不标准的。您确定不想改为在“完成”上执行此操作吗？

Answer 3

更简单的解决方案，您可以使用 self.navigationController?.viewControllers 访问以前的视图控制器，如下所示：

let vcsCount = self.navigationController?.viewControllers.count
self.navigationController?.viewControllers[vcsCount! - 2].updateData

updateData 是前一个视图控制器要更新的数据成员

Answer 4

另外，你可以使用这个扩展：

extension UINavigationController {
    func viewController<T: UIViewController>(class: T.Type) -> T? {

        return viewControllers.filter({$0 is T}).first as? T
    }
}

//

if let controller = navigationController?.viewController(class: MainViewController.self) {
     controller.data = data
}

navigationController?.popViewController(animated: true)