How to detect UIPageViewController reach the last page

How to detect the last page in pageViewController has been called and if I want to add a gesture recognizer on the last page and forward to my app main page, is there a way to do it?

Here is my basic pageViewController snippet, in my UIPageViewController viewDidLoad

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Create the data model
    _pageImages = @[@"intro_1@2x.png", @"intro_2@2x.png", @"intro_3@2x.png", @"intro_4@2x.png"];

    // Create page view controller
    self.pageViewController = [self.storyboard instantiateViewControllerWithIdentifier:@"RKYGuide"];
    self.pageViewController.dataSource = self;

    RKYGuideContentViewController *startingViewController = [self viewControllerAtIndex:0];
    NSArray *viewControllers = @[startingViewController];
    [self.pageViewController setViewControllers:viewControllers direction:UIPageViewControllerNavigationDirectionForward animated:NO completion:nil];

    [self addChildViewController:_pageViewController];
    [self.view addSubview:_pageViewController.view];
    [self.pageViewController didMoveToParentViewController:self];
}

also, implements two page view controller data source methods

- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerBeforeViewController:(UIViewController *)viewController
{
    NSUInteger index = ((RKYGuideContentViewController*) viewController).pageIndex;

    if ((index == 0) || (index == NSNotFound)) {
        return nil;
    }

    index--;
    return [self viewControllerAtIndex:index];
}

- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerAfterViewController:(UIViewController *)viewController
{
    NSUInteger index = ((RKYGuideContentViewController*) viewController).pageIndex;

    if (index == NSNotFound) {
        return nil;
    }

    index++;

    if (index == [self.pageImages count]) {
        // adding gesture
        pageViewController.view.userInteractionEnabled = YES;
        pageViewController.view.contentMode = UIViewContentModeScaleAspectFit;
        UITapGestureRecognizer *singleTap = [[UITapGestureRecognizer alloc]
                                             initWithTarget:self
                                             action:@selector(startAction)];
        [singleTap setNumberOfTapsRequired:1];
        pageViewController.view.userInteractionEnabled = YES;
        [pageViewController.view addGestureRecognizer:singleTap];

        return nil;
    }

    NSLog(@"index: %u", index);

    return [self viewControllerAtIndex:index];
}

it works fine, but i don't know where to add an gesture recognizer while reaches to the last page, and leads to my main page.

EDIT: I did adding gesture recognizer in viewControllerAfterViewController, but it won't work, no responding.