视图不显示另一个childViewController的ChildViewController

Question

我对iOS/Swift中的多层childViewControllers有一个问题。当前设置有三层，从最低到最高：

1. InfoViewController
2. SelectionViewController
3. MainViewController

InfoViewController有一个从XIB加载的视图。

SelectionViewController包含一个带有InfoViewController和UIButton的UIStackView。

MainViewController是顶级VC，通常嵌入到UINavigationController中.

问题

当我将InfoViewController和它的视图直接添加到MainViewController时，一切都很好。

func setupInfoViewControllerDirectlyOnMainVC () {
    addChildViewController(infoViewController)
    infoViewController.view.embedInside(otherView: infoContainerView)
    infoViewController.didMove(toParentViewController: self)
}

但是，如果我使用相同的方法将SelectionViewController添加到MainViewController中，则嵌入InfoViewController不会更新它的UI --它看起来总是像它正在控制的未触及的XIB文件。当它没有嵌入到这个系统中时，SelectionViewController的行为就像预期的那样。

如下图所示，UI是可见的，但是通过询问它的ViewController而对它所做的任何更改都不会出现--它看起来与它创建的XIB文件完全一样。

​

​

下面是以BasicInfoView开头的类设置，后面是上面列出的三个viewControllers。

BasicInfoView

class PLBasicInfoView: PLDesignableViewFromXib {

    //
    // MARK: Outlets
    //
    //

    @IBOutlet weak var photoView: PFRoundImageView!
    @IBOutlet weak var titleLabel: UILabel!
    @IBOutlet weak var subtitleLabel: UILabel!


    var imageFile:PFFile? {
        didSet {
            photoView.file = imageFile
            photoView.loadInBackground()
        }
    }

    //
    // MARK: Initialization
    //
    //

    override var nameOfXib: String {
        return "PLBasicInfoView"
    }

    override var intrinsicContentSize: CGSize {
        return CGSize(width: super.intrinsicContentSize.width, height: 56)
    }

}

BasicInfoViewController

class PLBasicInfoViewController: UIViewController {

    /**
     The BasicInfoView which will be managed by this controller.
     */
    var basicInfoView = PLBasicInfoView()

    /**
     This is the master stack view which contains all subviews.
     */
    var stackView = UIStackView()


    /**
     PFFile representing the image to be displayed in the imageView. Setting a valid imageFile object automatically laods the image from the server. If set to nil, the defaultImage is displayed instead.
     */
    var imageFile: PFFile? {
        didSet {
            if imageFile != nil {
                basicInfoView.imageFile = imageFile
            } else {
                basicInfoView.photoView.image = defaultImage
            }
        }
    }

    /**
     Default UIImage to be displayed in the imageView if there is no imageFile assigned.
     */
    var defaultImage: UIImage! {
        return #imageLiteral(resourceName: "ios7-camera-outline")
    }


    /**
     Main text of the infoView
     */
    var titleText:String? {
        didSet {
            basicInfoView.titleLabel.isHidden = (titleText == nil)
            basicInfoView.titleLabel.text = titleText
        }
    }

    /**
     Secondary text of the infoView. Displays under titleText.
     */
    var subtitleText:String? {
        didSet {
            basicInfoView.subtitleLabel.isHidden = (subtitleText == nil)
            basicInfoView.subtitleLabel.text = subtitleText
        }
    }

    /**
     Embed our stackView into main view. The custom embedInsider(otherView:UIView) method (UIView extension) will take care of the subview additional as well as all layout constraints.
     */
    func setupStackView () {
        stackView.embedInside(otherView: view)
        stackView.axis = .vertical
        stackView.addArrangedSubview(basicInfoView)
    }

    override
    func viewDidLoad() {
        super.viewDidLoad()
        setupStackView()
    }


}

SelectionViewController

class PLSelectableInfoViewController: UIViewController {


    /**
     If true, the info view will be shown and the selection button will be hidden.
     */
    var isAssigned = false {
        didSet {
            selectionButton.isHidden = isAssigned
            infoView.isHidden = !isAssigned
        }
    }


    /**
     The View controller dispaying the object in question.
     */
    var infoViewController: PLBasicInfoViewController! {
        return PLBasicInfoViewController()
    }

    private
    var infoView: UIView!

    /**
     Button on bottom of stack. Intended to allow user to assign a new value to the contact property.
     */
    var selectionButton = PLButton()

    /**
     Stack view containing all subviews.
     */
    var stackView = UIStackView()


    //
    // MARK: UIViewController Overrides
    //
    //

    override
    func viewDidLoad() {
        super.viewDidLoad()
        setupStackView()
        addInfoView()
    }


    private
    func setupStackView () {
        stackView.embedInside(otherView: view)
        stackView.axis = .vertical
    }

    private
    func addInfoView () {
        addChildViewController(infoViewController)
        infoView = infoViewController.view
        stackView.addArrangedSubview(infoView)
        infoViewController.didMove(toParentViewController: self)
    }

}

一些与此无关的代码已被删除。

Notes

请注意，在实践中，BasicInfoViewController和SelectionViewController都是子类。例如，我有一个ContactInfoViewController，它可以传递一个联系人对象并显示全名、公司名称和照片(如上所述，这很好)。还有一个SelectionViewController子类来补充这一点: ContactSelectionViewController。ContactSelectionViewController还有一个Contact对象属性，它可以被赋值，然后传递给嵌入的ContactInfoViewController --这是不显示数据的点。我已将这些子类包括在下面，以供参考。

ContactInfoViewController

同样，当直接放置到MainViewController中时，这是完美的。

class PLContactInfoViewController: PLBasicInfoViewController {

    /**
     Contact object managed by this controller.
     */
    var contact: PLContact? {
        didSet {
            if contact == nil {
                titleText = "Not Set"
                subtitleText = nil
                return
            }
            contact?.fetchIfNeededInBackground(block: { (object, error) in
                if let _ = object as? PLContact {
                    self.updateWithContact()
                }
            })
        }
    }

    override
    var defaultImage: UIImage! {
        return #imageLiteral(resourceName: "ios7-contact-outline")
    }


    private
    func updateWithContact () {
        if let c = contact {
            titleText = c.fullName
            imageFile = c.photo
            c.company?.fetchIfNeededInBackground(block: { (object, error) in
                if let comp = object as? PLCompany {
                    self.subtitleText = comp.name
                } else {
                    self.subtitleText = nil
                }
            })
        }
    }

}

ContactSelectionViewController

此VC功能正常，但嵌入式ContactInfoViewController不显示数据。由于某些原因，ContactInfoViewController的视图在此控制器内嵌入时不会使用数据进行更新。

class PLContactAssignmentViewController: PLSelectableInfoViewController {


    /**
     The contact currently selected by this contorller
     */
    var selectedContact: PLContact? {
        didSet {
            isAssigned = !(selectedContact == nil)
            contactInfoViewController.contact = selectedContact
        }
    }


    override
    var infoViewController: PLBasicInfoViewController! {
        return PLContactInfoViewController()
    }


    private
    var contactInfoViewController: PLContactInfoViewController {
        return infoViewController as! PLContactInfoViewController
    }

}

Answer 1

试一试

    var _infoViewController: PLBasicInfoViewController?
    var infoViewController: PLBasicInfoViewController! {
        if let vc = _infoViewController {
            return vc
        }
        _infoViewController = PLBasicInfoViewController()
        return _infoViewController!
    }

或

lazy var infoViewController: PLBasicInfoViewController = {
        return PLBasicInfoViewController()
    }()

这可能是因为每次尝试访问时都要启动PLBasicInfoViewController。