关闭时如何从模态视图控制器传回数据

Question

我已经按照here 的说明进行操作，但我仍然不确定这部分：

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

我尝试过以编程方式实例化视图控制器，但仍然无济于事。

这是我关闭模式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与模态视图进行衔接。

这是我希望传回父视图控制器的数据：

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

这是两个字符串值。

我尝试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是这样做的：

func sendValue(value: NSString) {
    receivedValue = value as String
}

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

当我点击打印按钮时，我仍然无法收到任何值。

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)
}

这是我没有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

根据您要传递的数据，您可以在呈现视图控制器中创建一个属性，您可以在关闭模态视图控制器时设置该属性，这样您就可以省去委托。

例如，您有一个ContactsViewController，拥有一个var contacts: [Contact] = [] 属性。当你想创建一个新的联系人时，你会展示一个带有不同值的模态视图控制器，你需要创建一个新的Contact 对象。当您完成并想要关闭视图控制器时，您可以像在代码中那样调用该函数，但在 ContactsViewController 中设置属性。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)
}

---

如果您不想想要使用委托，可以这样做：

在你的OOTDListViewController：

var testValue: String = ""

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

在您的模态视图控制器中（我称之为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)
}

如果您想要使用委托，可以这样做：

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)
    }
}

在你的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)
    }

}

Answer 2

我使用的是标签栏，所以工作代码如下：

if let tabBar = self.presentingViewController as? UITabBarController {
    let homeNavigationViewController = tabBar.viewControllers![0] as? UINavigationController
    let homeViewController = homeNavigationViewController?.topViewController as! HomeController
    homeViewController._transferedLocationID = self.editingLocationID!
}

Answer 3

需要在dismissViewController方法中调用委托方法

@IBAction func dismissViewController(_ sender: UIBarButtonItem) {
    delegate?.sendData(typeState: "top", categoryState: "casual")
    self.dismiss(animated: true) { 
        //
    }
 }

在你的 Modal ViewController 类中创建委托

weak var delegate: MyProtocol?

在 MyProtocol 和您分配委托的 presentingViewController 中创建一个方法名称为 sendData 的协议，实现 MyProtocol 方法

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

class ViewController: UIViewController, MyProtocol {
    var typeState: String?
    var categoryState: String?

    override func viewDidApear() {
        super.viewDidApear()
        presentNewModalVC()
    }
    
    func presentNewModalVC() {
       let modalVC = NewModalViewControllerToBePresented()
       modalVC.delegate = self
       present(modalVC, animated: true)
    }
    
    func sendData(typeState: String, categoryState: String) {
       self.typeState = typeState
       self.categoryState = categoryState
    }
 }

Answer 4

如果使用导航控制器，您必须首先获取 UINavigation 控制器，然后从导航控制器堆栈中获取正确的 ViewController。

这是我的代码在这种情况下的样子。

@IBAction func dismissViewController(_ sender: UIBarButtonItem) {
    if let navController = presentingViewController as? UINavigationController {
       let presenter = navController.topViewController as! OOTDListViewController
        presenter.testValue = "Test"
    }
    dismiss(animated: true, completion: nil)
}