关闭时如何从模态视图控制器传回数据

Question

我已按照此处的说明进行操作，但仍不确定这部分内容：

modalVC.delegate=self;
        self.presentViewController(modalVC, animated: true, completion: nil)

我曾尝试以编程方式实例化视图控制器，但仍然无济于事。

这是我退出模态视图控制器时的代码：

@IBAction func dismissViewController(_ sender: UIBarButtonItem) {
        self.dismiss(animated: true) { 
            //
        }
    }

我正在使用情节提要通过模式视图进行筛选。

这是我希望传输回父视图控制器的数据：

var typeState = "top"
 var categoryState = "casual"

这是两个字符串值。

编辑：

我试图从模态视图控制器传递数据，如下所示：

@IBAction func dismissViewController(_ sender: UIBarButtonItem) {
        self.dismiss(animated: true, completion: nil)
        delegate?.sendValue(value: "success")
        if let presenter = presentingViewController as? OOTDListViewController {
            presenter.receivedValue = "test"
        }
    }

而在父视图控制器上，我这样做的是：

func sendValue(value: NSString) {
        receivedValue = value as String
    }
  @IBAction func printReceivedValue(_ sender: UIButton) {
        print(receivedValue)
    }

当我按下打印按钮时，我仍然无法获得任何价值。

模态视图控制器：

protocol ModalViewControllerDelegate
{
    func sendData(typeState: String, categoryState: String)
}

var delegate:ModalViewControllerDelegate!

var typeState = "top"
var categoryState = "casual"
@IBAction func dismissViewController(_ sender: UIBarButtonItem) {
        self.dismiss(animated: true, completion: nil)
        delegate?.sendData(typeState: typeState as String, categoryState: categoryState as String)

    }

父视图控制器：

class parentViewController: UICollectionViewController, ModalViewControllerDelegate {

var typeState: String?
var categoryState: String?
func sendData(typeState: String, categoryState: String) {
        self.typeState = typeState as String
        self.categoryState = categoryState as String
    }
 @IBAction func printReceivedValue(_ sender: UIButton) {
     print(typeState)
 }

编辑：

这是我不使用委托方法的新代码：

模态视图控制器：

@IBAction func dismissViewController(_ sender: UIBarButtonItem) {
        self.dismiss(animated: true, completion: nil)
        if let presenter = presentingViewController as? OOTDListViewController {
            presenter.typeState = typeState
            presenter.categoryState = categoryState
        }
    }

OOTDListViewController：

@IBAction func presentModalView(_ sender: UIBarButtonItem) {
        let modalView = storyboard?.instantiateViewController(withIdentifier: "filterViewController") as! ModalViewController
        let navModalView: UINavigationController = UINavigationController(rootViewController: modalView)
        self.present(navModalView, animated: true, completion: nil)
    }
@IBAction func printValue(_ sender: UIButton) {
        print(typeState)
        print(categoryState)
    }

Answer 1

根据要传递的数据，您可以在呈现视图控制器中创建一个属性，可以在关闭模式视图控制器时进行设置，从而可以省去委托。

例如，您有一个ContactsViewController，持有一个var contacts: [Contact] = []属性。当您要创建一个新的联系人时，您将提供一个模态视图控制器，该控制器具有创建新Contact对象所需的不同值。完成并希望关闭视图控制器后，可以像在代码中一样调用该函数，但在中设置属性ContactsViewController。它看起来像这样：

@IBAction func dismissViewController(_ sender: UIBarButtonItem) {
    if let presenter = presentingViewController as? ContactsViewController {
        presenter.contacts.append(newContact)
    }
    dismiss(animated: true, completion: nil)
}

编辑：

如果你 不 希望使用一个委托，这是你如何去做：

在您的OOTDListViewController：

var testValue: String = ""

@IBAction func printReceivedValue(_ sender: UIButton) {
    print(testValue)
}

在您的模态视图控制器中（我称它为PresentedViewController）：

@IBAction func dismissViewController(_ sender: UIBarButtonItem) {
    // if your OOTDListViewController is part of a UINavigationController stack, this check will probably fail. 
    // you need to put a breakpoint here and check if the presentingViewController is actually a UINavigationController.
    // in that case, you will need to access the viewControllers variable and find your OOTDListViewController
    if let presenter = presentingViewController as? OOTDListViewController {
        presenter.testValue = "Test"
    }
    dismiss(animated: true, completion: nil)
}

如果 要 使用委托，请执行以下操作：

在您的OOTDListViewController中：

protocol ModalDelegate {
func changeValue(value: String)
}

class OOTDListViewController: ModalDelegate {

var testValue: String = ""
@IBAction func presentViewController() {
    // here, you either create a new instance of the ViewController by initializing it, or you instantiate it using a storyboard. 
    // for simplicity, I'll use the first way
    // in any case, you cannot use a storyboard segue directly, bevause you need access to the reference of the presentedViewController object
    let presentedVC = PresentedViewController() 
    presentedVC.delegate = self
    present(presentedVC, animated: true, completion: nil)
}

func changeValue(value: String) {
     testValue = value
     print(testValue)
}

}

在您的PresentedViewController：

class PresentedViewController {
    var delegate: ModalDelegate? 
    var testValue: String = ""

    @IBAction func dismissViewController(_ sender: UIBarButtonItem) {
       if let delegate = self.delegate {
            delegate.changeValue(testValue)
        }
        dismiss(animated: true, completion: nil)
    }

}