Avoid UIPageViewController "over-scrolling" - ios

Question

I have 2 VCs on my UIPageViewController.
I want that if the user is on the 1st view, he won't be able to swipe to the right (just to the left - to the 2nd view), and if he's on the 2nd view he won't be able to swipe to the left (just to the right - to the 1st view).
I want that the user won't be able to scroll - not a black view (what happens when I return nil on: - (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerBeforeViewController:(UIViewController *)viewController)

Answer 1

The "black view" is likely to be the background of your main view, or the background colour of your UIPageViewController.
You can kill scrolling in one of the directions depending on the ViewController that the PageViewController is currently showing
first set your VC as the delegate for the PageViewController's inner scroll view. You can add a more sophisticated subviews traversal here, this is a simple version:
for (UIView *view in self.pageViewController.view.subviews) {
if ([view isKindOfClass:[UIScrollView class]]) {
[(UIScrollView *)view setDelegate:self];
}
}
then add a property to your VC as this:
#property (nonatomic) CGPoint lastOffset;
and after that implement the following scroll view delegate methods
- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
scrollView.scrollEnabled = YES;
}
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView {
scrollView.scrollEnabled = YES;
self.lastOffset = scrollView.contentOffset;
}
- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
CGPoint nowOffset = scrollView.contentOffset;
NSLog(#"delta %f", self.lastOffset.x - nowOffset.x);
if ((self.lastOffset.x - nowOffset.x) < 0) {
//uncomment to prevent scroll to left
//scrollView.scrollEnabled = NO;
} else if ((self.lastOffset.x - nowOffset.x) > 0) {
//uncomment to prevent scroll to right
//scrollView.scrollEnabled = NO;
} else {
scrollView.scrollEnabled = YES;
}
}