[IOS][SWIFT] UIPageViewController 크래쉬

아래 처럼 죽는 경우가 발생

2017-02-22 13:29:28.984 PageTest[87046:5081125] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'The number of view controllers provided (3) doesn't match the number required (1) for the requested transition'

* 원인 

setViewControllers([vc1, vc2, vc3], direction: .forward, animated: false, completion: nil)

첫 번째 인자에 필요이상의 뷰컨트롤러를 할당함

* 수정

setViewControllers([vc1], direction: .forward, animated: false, completion: nil)

vc1만 할당 하고 나머지는 DataSource에서 처리 하도록 함

    public func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {

        guard let index = vcs.index(of: viewController)

            else { return nil }

        if index < 1 {

            return nil

        } else {

            return vcs[index - 1]

        }

    }

    public func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {

        guard let index = vcs.index(of: viewController)

            else { return nil }

        if index + 1 >= vcs.count {

            return nil

        } else {

            return vcs[index + 1]

        }

    }