import JRPageViewControllerKit

// 1. Create a factory that will return viewController for a specific index.
let factory: ((Int) -> ChildViewController?) = { [unowned self] index -> ChildViewController? in
    let viewController = self.storyboard!.instantiateViewController(withIdentifier: "ChildViewController") as! ChildViewController
    viewController.index = index
    return viewController
}

// 2. Instantiate a PageViewControllerManager.
let pageViewControllerManager = PageViewControllerManager(insertIn: containerView, inViewController: self, totalPages: 6, viewControllerForIndex: factory)

// 3. Get notified when user swiped to another viewController.
pageViewControllerManager.didScrollToIndex = { index in
    // The index that the user has just scrolled.
}

// 4. Get notified when another viewController is about to be appeared.
pageViewControllerManager.nextViewControllerAppears = { [unowned self] direction, ratio, destinationIndex in
    let ratio = String(format: "%.2f", ratio)
    let text = "direction:\(direction.rawValue), ratio:\(ratio),\n  to \(destinationIndex)"
}