so usually I would use a delegate pattern for this but this is a tricky situation.
View controller A presents -> view controller B which presents -> view controller C.
When the user finished the steps in view controller C, I will dismiss both B and C in one call with
self.presentingViewController?.presentingViewController?.dismiss(animated: true, completion: nil)
I would like to pass the data from view controller C back to A. How is this possible, since A has no reference to C, how can I implement a delegate?
****EDIT: This is all done programmatically, so I cant use unwind segues
***** SOLUTION *******
The best solution I found was to just add an observer in VC A and post the object in VC C when dismissing the VC:
self.presentingViewController?.presentingViewController?.dismiss(animated: true) {
NotificationCenter.default.post(name: Notification.Name("UpdateKeywords"), object: self.account)
}
Dont forget to remove the observer in VC A in deinit()
我通常要做的是在b中创建对A的引用,然后在C中创建对该引用的引用,然后在返回A之前,对引用进行更改,然后调用self.presentingViewController?.presentingViewController?.dismiss(animated: true, completion: nil)
you can use singleton design pattern. Declare a singleton class for datas.
class DatasSingleton{
static let sharedInstance = DatasSingletonSingleton()
var datas: int = 0
}
in class C you set data
class C{
func xyz(){
DatasSingleton.sharedInstance.datas = 6
}
}
in class A you can read data
class A{
func xyz(){
print(DatasSingleton.sharedInstance.datas)
}
}
The example code, VC A present VC B, VC B present VC C, at VC C you enter text, and then the method of VC A is called (here the data is transferred) with the text entered at VC C. See below...
Hope that helps
(Xcode 8.1 (8B62): Delete storyboard, launchscreen, Clean properties Main story board and Launchscreen in Info.plist and replace AppDelegate.swift with the following content)
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
}
}
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