Why won't my subVC from UIPageViewController pass data to my View Controller effectively using a closure instead of delegates?

问题

My homework project has a single RootVC with the top half of the page being a scrollable UIPageviewController object. The UIPageViewController has a sub-View Controller called SubVCOne.

Pressing a greeting button placed on SubVCOne presents a greeting View on the RootVC. I need too find a way to pass this information from the SubVCOne of the UIPageViewController to the RootVC w/o using protocols or delegates or caches; hence closures.

My attempts have been a little futile---

Root VC:

class RootVC: UIViewController {


let pagingContainer: UIView = {
    let view = UIView()
    view.backgroundColor = .white
    view.translatesAutoresizingMaskIntoConstraints = false
    return view
}()

override func viewDidLoad() {
    super.viewDidLoad()
    view.backgroundColor = .systemBlue
    view.addSubview(pagingContainer)

    SubVCOne().closureComm = { [weak self] in
        let greetingView = GreetingView()
        self?.view.addSubview(greetingView)
    }

    pagingContainer.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
    pagingContainer.widthAnchor.constraint(equalTo: view.widthAnchor, multiplier: 1).isActive = true
    pagingContainer.heightAnchor.constraint(equalTo: view.heightAnchor, multiplier: 0.5).isActive = true
    pagingContainer.bottomAnchor.constraint(equalTo: view.bottomAnchor).isActive = true

    let pageController = PageViewController(transitionStyle: .scroll, navigationOrientation: .horizontal)
           addChild(pageController)
           pageController.didMove(toParent: self)
           pageController.view.translatesAutoresizingMaskIntoConstraints = false
           pagingContainer.addSubview(pageController.view)

           pageController.view.heightAnchor.constraint(equalTo: pagingContainer.heightAnchor, multiplier: 1).isActive = true
           pageController.view.widthAnchor.constraint(equalTo: pagingContainer.widthAnchor, multiplier: 1).isActive = true

           pageController.view.topAnchor.constraint(equalTo: pagingContainer.topAnchor).isActive = true
           pageController.view.bottomAnchor.constraint(equalTo: pagingContainer.bottomAnchor).isActive = true
           pageController.view.leadingAnchor.constraint(equalTo: pagingContainer.leadingAnchor).isActive = true
           pageController.view.trailingAnchor.constraint(equalTo: pagingContainer.trailingAnchor).isActive = true
    }
}

The sub-ViewController of the UIPageVC:

class SubVCOne: UIViewController {

var closureComm: (() -> Void)?

let greetMeButton: UIButton = {
    let button = UIButton(type: .system)
    button.setTitle("Greet!", for: .normal)
    button.addTarget(self, action: #selector(acceptButtonPressed), for: .touchUpInside)
    button.translatesAutoresizingMaskIntoConstraints = false
    return button
}()

@objc func acceptButtonPressed() {
    print("Greet me button pressed")
    let greetingView = GreetingView()
    view.addSubview(greetingView)
    closureComm?()
}


override func viewDidLoad() {
    super.viewDidLoad()
    view.backgroundColor = .systemOrange
    view.addSubview(greetMeButton)
    greetMeButton.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
    greetMeButton.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true
}

}

My UIPageViewController:

class PageViewController: UIPageViewController {

    lazy var subViewControllers:[UIViewController] = {
        return [SubVCOne()]
    }()


    init(transitionStyle style:
        UIPageViewController.TransitionStyle, navigationOrientation: UIPageViewController.NavigationOrientation, options: [String : Any]? = nil) {
        super.init(transitionStyle: .scroll, navigationOrientation: .horizontal, options: nil)
    }



    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        dataSource = self
        delegate = self
        setViewControllerFromIndex(index: 0)
    }

    func setViewControllerFromIndex(index:Int) {
        self.setViewControllers([subViewControllers[index]], direction: UIPageViewController.NavigationDirection.forward, animated: true, completion: nil)
    }
}

extension PageViewController: UIPageViewControllerDelegate, UIPageViewControllerDataSource {
    func presentationCount(for pageViewController: UIPageViewController) -> Int {
        return subViewControllers.count
    }

    func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
        let currentIndex:Int = subViewControllers.firstIndex(of: viewController) ?? 0
        if currentIndex <= 0 {
            return nil
        }
        return subViewControllers[currentIndex-1]
    }

    func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
        let currentIndex:Int = subViewControllers.firstIndex(of: viewController) ?? 0
        if currentIndex >= subViewControllers.count-1 {
            return nil
        }
        return subViewControllers[currentIndex+1]
    }
}

来源：https://stackoverflow.com/questions/59444564/why-wont-my-subvc-from-uipageviewcontroller-pass-data-to-my-view-controller-eff

标签

ios

swift

closures