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Editorial Team
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Asked: 2026-06-15T21:14:28+00:00

I’m learning iOS programming from a book, and I’ve coded an app to make

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I’m learning iOS programming from a book, and I’ve coded an app to make a page turn to another page, similar to iBooks. But when I run it in the simulator, when I swipe to the left or right the page doesn’t turn or transition at all. I don’t know why.

My code that I believe is relevant is below. I’ve also attached the whole project in case I’ve missed anything. Basically there’s a UIWebview that is the content for the UIViewController. It gets populated from the model located in the class that acts as the data source for the PageView. Depending on which view controller you go to the appropriate (protocol) method then sets the content in the webview according to the index of the view controller you’re going to.

But, it won’t work, as said:

- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerBeforeViewController:(UIViewController *)viewController {
    NSUInteger index = [self indexOfViewController:(ContentViewController *)viewController];

    if (index == 0 || index == NSNotFound) {
        return nil;
    }
    else {
        index--;
        return [self viewControllerAtIndex:index];
    }
}

- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerAfterViewController:(UIViewController *)viewController {
    NSUInteger index = [self indexOfViewController:(ContentViewController *)viewController];

    if (index == NSNotFound) {
        return nil;
    }
    else {
        index--;
        return [self viewControllerAtIndex:index];
    }
}


- (void)viewDidLoad {
    [super viewDidLoad];
    [self createContentPages];

    NSDictionary *options = [NSDictionary dictionaryWithObject:[NSNumber numberWithInteger:UIPageViewControllerSpineLocationMin]
        forKey:UIPageViewControllerOptionSpineLocationKey];

    _pageController = [[UIPageViewController alloc] initWithTransitionStyle:UIPageViewControllerTransitionStylePageCurl
        navigationOrientation:UIPageViewControllerNavigationOrientationHorizontal
        options: options];

    _pageController.dataSource = self;
    [[_pageController view] setFrame:[[self view] bounds]];

    ContentViewController *initialViewController = [self viewControllerAtIndex:0];

    NSArray *viewControllers = [NSArray arrayWithObject:initialViewController];

    [_pageController setViewControllers:viewControllers direction:UIPageViewControllerNavigationDirectionForward
        animated:NO
        completion:nil];

    [self addChildViewController:_pageController];

    [[self view] addSubview:[_pageController view]];

    [_pageController didMoveToParentViewController:self];
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (void)createContentPages {
    NSMutableArray *pageStrings = [[NSMutableArray alloc] init];

    for (int i = 1; i <= 10; i++) {
        NSString *contentString = [[NSString alloc] initWithFormat:@"<html><head></head><body><h1>Chapter %d</h1><p>This is the page %d of content displayed using UIPageViewController in iOS 6.</p></body></html>", i, i];
        [pageStrings addObject:contentString];
    }

    self.pageContent = [[NSArray alloc] initWithArray:pageStrings];
}

// Return the data view controller for the given index
- (ContentViewController *)viewControllerAtIndex:(NSUInteger)index {
    if (([self.pageContent count] == 0) || index >= [self.pageContent count]) {
        return nil;
    }
    else {
        UIStoryboard *storyBoard = [UIStoryboard storyboardWithName:@"MainStoryboard" bundle:[NSBundle mainBundle]];

        ContentViewController *dataViewController = [storyBoard instantiateViewControllerWithIdentifier:@"contentView"];

        dataViewController.dataObject = self.pageContent[index];

        return dataViewController;
    }
}

- (NSUInteger)indexOfViewController:(ContentViewController *)viewController {
    return [self.pageContent indexOfObject:viewController.dataObject];
}

Whole project: http://cl.ly/1B0l3Z1H1616

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1 Answer

  1. Editorial Team

    In the

    - (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerAfterViewController:(UIViewController *)viewController

    method, you have

    index--

    Try changing it to

    index++
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