UIPageViewControllerで無限にループさせたい

UIPageViewControllerDataSourceでViewControllerを返すときに、先頭と末尾をくっつければよし。
XCodeのサンプルコードのModelController.mを↓とする。

ModelController.m

#pragma mark - Page View Controller Data Source

- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerBeforeViewController:(UIViewController *)viewController
{
    NSUInteger index = [self indexOfViewController:(DataViewController *)viewController];
    if( index == NSNotFound){
        return nil;
    }
    if (index == 0) {
        // 先頭に行ってたら最後のControllerを返す（＝ループ）
        index = [self.pageData count]-1;
    }else{
        index--;
    }
    return [self viewControllerAtIndex:index storyboard:viewController.storyboard];
}

- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerAfterViewController:(UIViewController *)viewController
{
    NSUInteger index = [self indexOfViewController:(DataViewController *)viewController];
    if (index == NSNotFound) {
        return nil;
    }
    
    index++;
    if (index == [self.pageData count]) {
        // 末尾に行ってたら先頭のControllerを返す（＝ループ）
        index = 0;
    }
    return [self viewControllerAtIndex:index storyboard:viewController.storyboard];
}