Is there a way to override the viewControllerBefore / After methods in UIPageViewControllerDataSource to avoid repeating code?

Question

I've created several PageViewControllers throughout an app and they all require some of the same configuration, so I was wondering if there's a way to override the methods or do this in a cleaner way.

Right now, for every one of the 4 I created, I have the following setup code. The only variable is the array of viewControllers (which is declared in the PageViewController class), otherwise this code has to be repeated 4 times.

extension ThemeSelector: UIPageViewControllerDataSource {

func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
    guard let currentIndex = themes.firstIndex(of: viewController) else { return nil }

    // This is used to prevent the pageViewController from trying to instantiate a vc before that doesn't exist.
    if currentIndex > 0 { return themes[currentIndex - 1] }
    else { return nil }
}

func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
    guard let currentIndex = themes.firstIndex(of: viewController) else { return nil }

    // This is used to prevent the pageViewController from trying to instantiate a vc after that doesn't exist.
    if currentIndex < themes.count - 1 { return themes[currentIndex + 1] }
    else { return nil}
}


// MARK: Pagination Dots
func presentationCount(for _: UIPageViewController) -> Int {
    return themes.count
}

func presentationIndex(for _: UIPageViewController) -> Int {
    guard let firstViewController = viewControllers?.first,
        let firstViewControllerIndex = themes.firstIndex(of: firstViewController) else {
            return 0
    }
    return firstViewControllerIndex
}

}

Thanks in advance.

Answer 1

You can create BasePageViewController with this setup code and inherit.