UIPageViewController transition 'Unbalanced calls to begin/end appearance transitions for '

Question

When I navigate through UIPageViewController faster than its transition animation I am getting \'Unbalanced calls to begin/end appearance transitions for <

Answer 1

Here's the Swift version of Bill Cheswick's answer (currently the top answer):

Add a variable to hold the current state:

var pageIsAnimating = false

Set the animating state:

func pageViewController(pageViewController: UIPageViewController, willTransitionToViewControllers pendingViewControllers: [UIViewController]) {
    self.pageIsAnimating = true
}

func pageViewController(pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {
    if finished || completed {
        self.pageIsAnimating = false
    }
}

Block the transitions if it's currently animating:

func pageViewController(pageViewController: UIPageViewController, viewControllerBeforeViewController viewController: UIViewController) -> UIViewController? {
    if self.pageIsAnimating {
        return nil
    }

    // Your code here
}

func pageViewController(pageViewController: UIPageViewController, viewControllerAfterViewController viewController: UIViewController) -> UIViewController? {
    if self.pageIsAnimating {
        return nil
    }

    // Your code here
}

Thank you Bill Cheswick!