orderedViewControllers

The orderedViewControllers: [UIViewController] variable contains a generated list of the view controllers to be used in a UIPageViewController. The view controllers are displayed in the order in which they appear in the list returned by the orderedViewControllers variable.

private(set) var orderedViewControllers: [UIViewController] = {
    func newViewController(_ name: String) -> UIViewController {
      	return UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "page")
    }
    let viewOrder = ["page1", "page2", "page3"]
    let controllers = viewOrder.map { newViewController($0) }
    return controllers
}()

The above example uses a scoped function newViewController(_:) -> UIViewController to instantiate a new view controller using the storyboard identifier page. viewOrder.map { newViewController($0) } assigns a new list of view controllers to the controllers variable using the strings in viewOrder. Notice, however, that these strings are never passed to the newly instantiated view controllers. The below example shows how to send the data to a view controller, though this is not a necessary requirement of the UIPageViewController.

// Assume pages use a view controller similar to this
class ViewController: UIViewController {
    var title: String = "default value"

    // rest of view controller declaration
}

class PageViewController: UIPageViewController {
    private(set) var orderedViewControllers: [UIViewController] = {
        func newViewController(_ name: String) -> UIViewController {
            return UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "page")
        }
        let viewOrder = ["page1", "page2", "page3"]
        let controllers = viewOrder.map { newViewController($0) as! ViewController }
        for i in 0 ..< controllers.count {
            controllers[i].page = viewOrder[i]
        }
        return controllers
    }()

    // rest of page view controller declaration
}