Pass variable from UIPageViewController to UIViewController child

Question

I am trying to create a tutorial / intro for my app and since at this point I am not sure how many pages will it have I decided to use a UIPageViewController with a single child.

My intention is to store all the data I wanna display in an object array and to use the index of the current displayed view inside my UIPageViewController to get the object I need from that array.

override func viewWillAppear(_ animated: Bool)
{
    print("PageContentVC > viewWillAppear")

    ivPageContent.image = UIImage(named: DataSingleton.sharedInstance.returnTutorialVCContent()[contentPage].contentImage!)
    lblPageContentTitle.text = DataSingleton.sharedInstance.returnTutorialVCContent()[contentPage].contentLabel!
    lblPageContentText.text = DataSingleton.sharedInstance.returnTutorialVCContent()[contentPage].contentText!
}

For this I need to pass that index from my UIPageViewController to its child, ContentPageVC. I have no problem in getting the index but I am having difficulties passing it to ContentPageVC.

import UIKit

class TutorialPageVC : UIPageViewController,
    UIPageViewControllerDataSource,
    UIPageViewControllerDelegate
{
    /*
    // MARK: - Variables & Constants
    */

    var contentPage : Int = 0
    var collectionViewPageControl : UIPageControl = UIPageControl()

    lazy var pagesArray : [UIViewController] =
    {
        return [self.VCInstance(name: "pageContent"),
                self.VCInstance(name: "pageContent"),
                self.VCInstance(name: "pageContent"),
                self.VCInstance(name: "pageContent"),
                self.VCInstance(name: "pageContent"),
                self.VCInstance(name: "pageContent"),
                self.VCInstance(name: "pageContent"),
                self.VCInstance(name: "pageContent"),
                self.VCInstance(name: "pageContent")]
    }()

    private func VCInstance(name: String) -> UIViewController
    {
        return UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: name)
    }


    /*
    // MARK: - VC Status
    */

    override func viewDidLoad()
    {
        super.viewDidLoad()

        print("TutorialPageVC > viewDidLoad")

        self.dataSource = self
        self.delegate = self

        if let firstVC = pagesArray.first
        {
            setViewControllers([firstVC], direction: .forward, animated: true, completion: nil)
        }

        let pageControl = UIPageControl.appearance()
        pageControl.currentPageIndicatorTintColor = UIColor.activeColor
        pageControl.pageIndicatorTintColor = UIColor.backgroundColor
        self.view.backgroundColor = UIColor.clear
    }

    override func viewDidLayoutSubviews()
    {
        super.viewDidLayoutSubviews()

        print("TutorialPageVC > viewDidLayoutSubviews")

        for view in self.view.subviews
        {
            if view is UIScrollView { view.frame = UIScreen.main.bounds }
        }
    }

    /*
    // MARK: - UIPageViewController Delegates
    */

    public func pageViewController(_ pageViewController: UIPageViewController,
                                   viewControllerBefore viewController: UIViewController) -> UIViewController?
    {
        print("TutorialPageVC > pageViewController > viewControllerBefore")

        guard let viewControllerIndex = pagesArray.firstIndex(of: viewController) else { return nil }

        let previousIndex = viewControllerIndex - 1

        guard previousIndex >= 0 else { return pagesArray.last }
        guard pagesArray.count > previousIndex else { return nil }

        return pagesArray[previousIndex]
    }

    public func pageViewController(_ pageViewController: UIPageViewController,
                                   viewControllerAfter viewController: UIViewController) -> UIViewController?
    {
        print("TutorialPageVC > pageViewController > viewControllerAfter")

        guard let viewControllerIndex = pagesArray.firstIndex(of: viewController) else { return nil }

        let nextIndex = viewControllerIndex + 1

        guard nextIndex < pagesArray.count else { return pagesArray.first }
        guard pagesArray.count > nextIndex else { return nil }

        return pagesArray[nextIndex]
    }

    public func presentationCount(for pageViewController: UIPageViewController) -> Int
    {
        print("TutorialPageVC > presentationCount")

        return pagesArray.count
    }

    public func presentationIndex(for pageViewController: UIPageViewController) -> Int
    {
        print("TutorialPageVC > presentationIndex")

        guard let firstViewController = viewControllers?.first,
              let firstViewControllerIndex = pagesArray.firstIndex(of: firstViewController) else
        {
            return 0
        }

        return firstViewControllerIndex
    }

    public func pageViewController(_ pageViewController: UIPageViewController,
                                   willTransitionTo pendingViewControllers: [UIViewController])
    {
        print("TutorialPageVC > pageViewController > willTransitionTo")
    }

    public func pageViewController(_ pageViewController: UIPageViewController,
                                   didFinishAnimating finished: Bool,
                                   previousViewControllers: [UIViewController],
                                   transitionCompleted completed: Bool)
    {
        print("TutorialPageVC > pageViewController > didFinishAnimating")

        if completed
        {
            if let currentViewController = pageViewController.viewControllers?.first,
               let index = pagesArray.firstIndex(of: currentViewController)
            {
                contentPage = index
                print(contentPage)
            }
        }
    }
}

I've been looking for some time now for a solution and I found these:

PageViewController pass data to child controller

Passing data between UIPageViewController Child views with Swift

PageViewController - Pass variables to child views

how to pass data from UIPageViewController to child ViewController using delegates

I know this is a common issue but unfortunately none of the solutions I found worked for me and I fail to see why and what I'm missing.

Any ideas?

score 0 · Answer 1 · answered Jun 18 '19 at 09:33

0

Replace

return pagesArray[previousIndex]

with

let item =  pagesArray[previousIndex]
item.index = previousIndex
return item

and so on for next

class VCInstance:UIViewController {
   var index:Int!
}

Also

lazy var pagesArray : [UIViewController] =

with

lazy var pagesArray : [VCInstance] =

answered Jun 18 '19 at 09:33

Shehata Gamal

98,760
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I get "Cannot assign to value: 'index' is a method" when replacing return pagesArray[previousIndex] with what you suggested. – daydr3am3r Jun 18 '19 at 09:45

Pass variable from UIPageViewController to UIViewController child

1 Answers1