如何将数据传回给模态视图控制器
所以通常我会使用委托模式，但这是一个棘手的情况。
视图控制器A呈现 – >视图控制器B呈现 – >视图控制器C.
当用户完成视图控制器C中的步骤时，我将在一次通话中解除B和C.
self.presentingViewController?.presentingViewController?.dismiss(animated: true, completion: nil) 我想将视图控制器C中的数据传递回A.这怎么可能，因为A没有引用C，我怎样才能实现一个委托？
****编辑：这一切都以编程方式完成，所以我不能使用unwind segues
*****解决scheme*******
我发现的最好的解决办法是在VC A中添加一个观察者，并在closuresVC时在VC C中发布该对象：
self.presentingViewController?.presentingViewController?.dismiss(animated: true) { NotificationCenter.default.post(name: Notification.Name("UpdateKeywords"), object: self.account) }
不要忘记在deinit（）中删除VC A中的观察者
我通常会做的是在b中创build一个引用A，然后在C中创build对引用的引用，然后在传回给A之前，对引用进行更改，然后调用self.presentingViewController?.presentingViewController?.dismiss(animated: true, completion: nil)
你可以使用单身devise模式。 为数据声明一个单例类。
class DatasSingleton{ static let sharedInstance = DatasSingletonSingleton() var datas: int = 0 }
在C类你设置数据
class C{ func xyz(){ DatasSingleton.sharedInstance.datas = 6 } }
在Aclass你可以读取数据
class A{ func xyz(){ print(DatasSingleton.sharedInstance.datas) } }
示例代码VC A呈现VC B，VC B呈现VC C，在VC C处input文本，然后调用VC A的方法（此处传输数据），VC C中input的文本如下所示。 ..
希望有所帮助
（Xcode 8.1（8B62）：删除故事板，启animation面，清理属性Info.plist中的主要故事板和启animation面，并将AppDelegate.swiftreplace为以下内容）
import UIKit @UIApplicationMain class AppDelegate: UIResponder, UIApplicationDelegate { var window: UIWindow? func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool { self.window = UIWindow(frame: UIScreen.main.bounds) self.window!.rootViewController = Avc() self.window!.makeKeyAndVisible() return true } } class Avc: UIViewController { override func viewDidLoad() { super.viewDidLoad() let b = self.view.addSubviewWithConstraints(["b" : Button(title: "Open B VC")], constraints: ["V:|-10-[b(70)]", "H:|-10-[b]-10-|"])["b"] (b as! Button).action = {() in let bvc = Bvc() bvc.action = self.receiveData self.present(bvc, animated: false,completion: nil) } } func receiveData(data: String?) { print(data) } } class Bvc: UIViewController { var action: ((_ data: String?)->())! override func viewDidLoad() { super.viewDidLoad() let b = self.view.addSubviewWithConstraints(["b" : Button(title: "Open C VC")], constraints: ["V:|-10-[b(70)]", "H:|-10-[b]-10-|"])["b"] (b as! Button).action = {() in let cvc = Cvc() cvc.action = self.action self.present(cvc, animated: false,completion: nil) } } } class Cvc: UIViewController { var action: ((_ data:String?)->())! override func viewDidLoad() { super.viewDidLoad() let t = self.view.addSubviewWithConstraints(["t" : UITextField()], constraints: ["V:|-50-[t(24)]", "H:|-10-[t]-10-|"])["t"] (t as! UITextField).backgroundColor = UIColor.white let b = self.view.addSubviewWithConstraints(["b" : Button(title: "Transfer data to A VC")], constraints: ["V:|-100-[b(90)]", "H:|-10-[b]-10-|"])["b"] (b as! Button).action = {() in self.presentingViewController?.dismiss(animated: true, completion: nil) self.presentingViewController?.presentingViewController?.dismiss(animated: true, completion: nil) self.action((t as! UITextField).text) } } } class Button: UIButton { var action: (()->())! init(title: String) { super.init(frame : CGRect.zero) self.setTitle(title, for: UIControlState()) self.addTarget(self, action: #selector(Button.buttonAction(_:)), for: .touchUpInside) } required init?(coder: NSCoder) {super.init(coder: coder)} func buttonAction(_ sender: AnyObject) {if action != nil {action()}} } extension UIView { func addSubviewWithConstraints(_ views: [String : AnyObject], constraints: Array<String>) -> [String : AnyObject] { for (_, view) in views { self.addSubview(view as! UIView) (view as! UIView).translatesAutoresizingMaskIntoConstraints = false } for i in 0 ..< constraints.count {self.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: constraints[i], options: NSLayoutFormatOptions(rawValue: 0), metrics: nil, views: views))} return views } }