App crashes with error message empty array - iphone

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

From what I can see here, it looks like you initialize modelArray before you have a number for totalPages, since this is only set in initWithPDFAtPath. Although I think you can (and should) reorganize the code so that only one of the view controllers has to manage the page numbers, you can probably fix the issue by moving the line
AViewController *aViewController = [[AViewController alloc] initWithPDFAtPath:path];
to before the point where you initialize modelArray.
Hope this helps!

Answer 2

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.