App crashes with error message empty array

Question

Have initwithPDFAtPath in AViewController

-(id)initWithPDFAtPath:(NSString *)path {

NSURL *pdfUrl = [NSURL fileURLWithPath:path];
thePDF = CGPDFDocumentCreateWithURL((__bridge CFURLRef)pdfUrl);
totalPages = (int)CGPDFDocumentGetNumberOfPages(thePDF);

self = [super initWithNibName:nil bundle:nil];
return self;

 }

Trying to open pdf file in BViewController using viewDidLoad method

 - (void)viewDidLoad {

[super viewDidLoad];

//modelArray holds the page numbers

modelArray = [[NSMutableArray alloc] init];

for (int index = 1; index <= totalPages; index++) {

[modelArray addObject:[NSString stringWithFormat:@"%i", index]];

}
thePageViewController = [[UIPageViewController alloc] initWithTransitionStyle:UIPageViewControllerTransitionStylePageCurl navigationOrientation: UIPageViewControllerNavigationOrientationHorizontal options:nil];

thePageViewController.delegate = self;
thePageViewController.dataSource = self;

thePageViewController.view.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
NSString *path = [[NSBundle mainBundle] pathForResource:@"pages" ofType:@"pdf"];

NSURL *pdfurl = [NSURL fileURLWithPath:path];
PDFDocument = CGPDFDocumentCreateWithURL((__bridge CFURLRef)pdfurl);
AViewController = [[AViewController alloc] initWithPDFAtPath:path];
aViewController.page = [modelArray objectAtIndex:0];
NSArray *viewControllers = [NSArray arrayWithObject:aViewController];

}

When i execute it crashes with empty array message. Terminating app due to uncaught exception 'NSRangeException', reason: '* -[__NSArrayM objectAtIndex:]: index 0 beyond bounds for empty array'

EDIT:

AViewController has a PDFScrollview

   - (void)viewDidLoad
  {
[super viewDidLoad];

// Create our PDFScrollView and add it to the view controller.
CGPDFPageRef PDFPage = CGPDFDocumentGetPage(thePDF, [_page intValue]);

pdfScrollView = [[PDFScrollView alloc] initWithFrame:CGRectMake(0, 0, self.view.bounds.size.width, 925)];
[pdfScrollView setPDFPage:PDFPage];

[self.view addSubview:pdfScrollView];
  }

Answer 1

It sounds to me that totalPages could not be initialised in BViewController.

Also Not sure how you store it, as in AViewController you do initialisation of this variable before calling super init which could lead to loosing this value.

To fix this I think you need do couple of things.

First in AViewContoller change init method to something like this:

-(id)initWithPDFAtPath:(NSString *)path {

    self = [super initWithNibName:nil bundle:nil];
    if (self) {
        NSURL *pdfUrl = [NSURL fileURLWithPath:path];
        _thePDF = CGPDFDocumentCreateWithURL((__bridge CFURLRef)pdfUrl);
        _totalPages = (int)CGPDFDocumentGetNumberOfPages(thePDF);
    }

    return self;
 }

and store totalPages in parameters.

Than in BViewController you need to do

- (void)viewDidLoad {

   [super viewDidLoad];

//modelArray holds the page numbers

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

thePageViewController.delegate = self;
thePageViewController.dataSource = self;

thePageViewController.view.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
NSString *path = [[NSBundle mainBundle] pathForResource:@"pages" ofType:@"pdf"];

NSURL *pdfurl = [NSURL fileURLWithPath:path];
PDFDocument = CGPDFDocumentCreateWithURL((__bridge CFURLRef)pdfurl);
AViewController = [[AViewController alloc] initWithPDFAtPath:path];

modelArray = [[NSMutableArray alloc] init];

if (aViewController.totalPages > 0) {
   for (int index = 1; index <= aViewController.totalPages; index++) {

     [modelArray addObject:[NSString stringWithFormat:@"%i", index]];

       }

       aViewController.page = [modelArray objectAtIndex:0];
   }

        NSArray *viewControllers = [NSArray arrayWithObject:aViewController];
    }

But really that seems some obvious problems with all Controllers Architecture.