Swift: UIPageViewController - Load separate views

Assuming you have view controllers 1-4 defined in the same storyboard as your UIPageViewController, and you have their Storyboard IDs set as ViewController0, ViewController1, and et cetera, then create a method to populate your view controller array and call it in your viewDidLoad() before calling createPageViewController()

    override func viewDidLoad() {
        super.viewDidLoad()
        populateControllersArray()
        createPageViewController()
        setupPageControl()
    }

Implement the method like so:

    var controllers = [PageItemController]()

    func populateControllersArray() {
        for i in 0...3 {
            let controller = storyboard!.instantiateViewControllerWithIdentifier("ViewController\(i)") as PageItemController
            controller.itemIndex = i
            controllers.append(controller)
        }
    }

And define your createPageViewController() as the following

    private func createPageViewController() {

        let pageController = self.storyboard!.instantiateViewControllerWithIdentifier("PageController") as UIPageViewController
        pageController.dataSource = self

        if !controllers.isEmpty {
            pageController.setViewControllers([controllers[0]], direction: UIPageViewControllerNavigationDirection.Forward, animated: false, completion: nil)
        }

        pageViewController = pageController
        addChildViewController(pageViewController!)
        self.view.addSubview(pageViewController!.view)
        pageViewController!.didMoveToParentViewController(self)
    }

then in your two delegate before and after methods:

    func pageViewController(pageViewController: UIPageViewController, viewControllerBeforeViewController viewController: UIViewController) -> UIViewController? {
        if let controller = viewController as? PageItemController {
            if controller.itemIndex > 0 {
                return controllers[controller.itemIndex - 1]
            }
        }
        return nil
    }
    func pageViewController(pageViewController: UIPageViewController, viewControllerAfterViewController viewController: UIViewController) -> UIViewController? {
        if let controller = viewController as? PageItemController {
            if controller.itemIndex < controllers.count - 1 {
                return controllers[controller.itemIndex + 1]
            }
        }
        return nil
    }

And in the count method

    func presentationCountForPageViewController(pageViewController: UIPageViewController) -> Int {
        return controllers.count
    }

---

In fact, you can populate controllers with any view controllers you want to display, just set their class as PageItemController in storyboard (in order to have index property).

Or you can set each view controller as it's own class, and use runtime property getting and setting.

Use controller.valueForKey("itemIndex") as Int in the before and after method instead of controller.itemIndex

Use controller.setValue(i, forKey: "itemIndex") instead of controller.itemIndex = i in populateControllersArray().

Just ensure that each controller class has the Int property itemIndex, or your application will crash.

To bring it all together in your code, do the following:

import UIKit

import UIKit

class ViewController: UIViewController, UIPageViewControllerDataSource {

    // MARK: - Variables
    private var pageViewController: UIPageViewController?

    // MARK: - View Lifecycle
    override func viewDidLoad() {
        super.viewDidLoad()
        populateControllersArray()
        createPageViewController()
        setupPageControl()
    }

    var controllers = [PageItemController]()


    func populateControllersArray() {
        for i in 0...3 {
            let controller = storyboard!.instantiateViewControllerWithIdentifier("ViewController\(i)") as PageItemController
            controller.itemIndex = i
            controllers.append(controller)
        }
    }

    private func createPageViewController() {

        let pageController = self.storyboard!.instantiateViewControllerWithIdentifier("PageController") as UIPageViewController
        pageController.dataSource = self

        if !controllers.isEmpty {
            pageController.setViewControllers([controllers[0]], direction: UIPageViewControllerNavigationDirection.Forward, animated: false, completion: nil)
        }

        pageViewController = pageController
        addChildViewController(pageViewController!)
        self.view.addSubview(pageViewController!.view)
        pageViewController!.didMoveToParentViewController(self)
    }

    private func setupPageControl() {
        let appearance = UIPageControl.appearance()
        appearance.pageIndicatorTintColor = UIColor.grayColor()
        appearance.currentPageIndicatorTintColor = UIColor.whiteColor()
        appearance.backgroundColor = UIColor.darkGrayColor()
    }

    // MARK: - UIPageViewControllerDataSource
    func pageViewController(pageViewController: UIPageViewController, viewControllerBeforeViewController viewController: UIViewController) -> UIViewController? {
        if let controller = viewController as? PageItemController {
            if controller.itemIndex > 0 {
                return controllers[controller.itemIndex - 1]
            }
        }
        return nil
    }
    func pageViewController(pageViewController: UIPageViewController, viewControllerAfterViewController viewController: UIViewController) -> UIViewController? {
        if let controller = viewController as? PageItemController {
            if controller.itemIndex < controllers.count - 1 {
                return controllers[controller.itemIndex + 1]
            }
        }
        return nil
    }

    // MARK: - Page Indicator

    func presentationCountForPageViewController(pageViewController: UIPageViewController) -> Int {
        return controllers.count
    }

    func presentationIndexForPageViewController(pageViewController: UIPageViewController) -> Int {
        return 0
}