swift - 根据最近关于用于在 VC 之间传递数据的闭包的问题，​​在 rootVC 中使用 containerVC 时我将如何做同样的事情？

Question

我看到了一个最近的赏金问题（如果你想看的话，可以找到链接）关于使用闭包在 VC 之间传递数据，其中一个 VC 嵌入在导航控制器中。虽然使用闭包相当容易，因为两个 VC 之间有一个直接的接触点（以 segue 的形式），但我一直想知道如果不是这种情况，它会如何工作。

例如，考虑以下设置（类似于启发本文的 OG 问题）：

RootVC，它有一个计数器 UILabel

一个 subContainer VC，它占据 RootVC 的下半部分，它有一个按钮，按下它应该将 RootVC 上的 UILabel 增加一。

我准备了如下代码（其中一些代码取自 OG 问题）：

根VC：

class RootVC: UIViewController {

    var tappedCount: Int = 0

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

    lazy var label: UILabel = {
        let label = UILabel()
        label.text = "\(tappedCount)"
        label.textAlignment = .center
        label.font = UIFont(name: "Copperplate", size: 90)
        label.translatesAutoresizingMaskIntoConstraints = false
        return label
    }()

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

        pagingContainer.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
        pagingContainer.widthAnchor.constraint(equalTo: view.widthAnchor, multiplier: 1).isActive = true
        pagingContainer.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor, constant: 0).isActive = true
        pagingContainer.heightAnchor.constraint(equalToConstant: 500).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


        label.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true


 label.bottomAnchor.constraint(equalTo: pagingContainer.topAnchor).isActive = true     
          }
       }

子容器VC：

class SubContainerVC: UIViewController {

    var callback : (() -> Void)?

    let button: UIButton = {
        let button = UIButton()
        button.setTitle("Button!", for: .normal)
        button.translatesAutoresizingMaskIntoConstraints = false
        button.addTarget(self, action: #selector(buttonPressed), for: .touchUpInside)
        button.backgroundColor = .green
        return button
    }()

    @objc func buttonPressed(_ sender: UIButton) {
        print("Hello")
        //Pressing this button should increment the label on RootVC by one.
    }

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

        button.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
        button.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true
    }

}

和 PageViewController 快速文件：

class PageViewController: UIPageViewController {

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


    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]
    }
}

标签： swift

Answer 1

您可以将闭包下游注入到SubContainerVC，这将导致闭包执行出现在上游。

类似的东西（只保留相关的 VC 代码）：

class SubContainerVC {
    var buttonCallback: () -> Void = { }

    @objc func buttonPressed(_ sender: UIButton) {
        print("Hello")
        buttonCallback()
    }
}

class PageViewController: UIViewController {

    // Note that you don't need the extra closure call for lazy vars 
    lazy var subViewControllers = [SubContainerVC()] {
        didSet {
            // just in case the controllers might change later on
            subViewControllers.forEach { $0.buttonCallback = buttonCallback }
        }
    }

    var buttonCallback: () -> Void = { } {
        didSet { 
            subViewControllers.forEach { $0.buttonCallback = buttonCallback }
        }
    }
}

class RootVC: UIViewController {

    var tappedCount: Int = 0 {
        didSet { 
            label.text = "\(tappedCount)"
        }
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        let pageController = PageViewController(transitionStyle: .scroll, navigationOrientation: .horizontal)
        // this will trigger the `didSet` from PageViewController, resulting
        // in the callback being propagated downstream
        pageController.buttonCallback = { self.tappedCount += 1 }
    }
}