Issue with [array count]

Question

I am a problem with counting values in a plist file ,the problem is the if statement should check if the value is greater than objects in my plist , then stop moving to next pages , here is my code but :

    picturesDictionary = [NSDictionary dictionaryWithContentsOfFile:
                                    [[NSBundle mainBundle] pathForResource:@"images" ofType:@"plist"]];  
arrays = [picturesDictionary objectForKey:@"PhotosArray"];

    int photoCount =  [arrays count];


if ((photoNumber < 1) || (photoNumber > photoCount)) return nil;

controller = [BookController rotatableViewController];

PhotosInAlbum.image = [UIImage imageNamed:[arrays objectAtIndex:pageNumber]];

but after when photos reach to the last page , application will crash , debugger message :

'NSRangeException', reason: '-[__NSCFArray objectAtIndex:]: index (30) beyond bounds (30)'
*** First throw call stack:

[NSArray count] gives you the number of items in the array, not the index of the last item. — Manuel
– Manuel, Commented Jun 1, 2012 at 12:46

Zoe - Save the data dump · Accepted Answer · 2019-05-26 12:20:46Z

5

try

if ((pageNumber < 0) || (pageNumber > (photoCount-1))) return nil;

the reason it crashes is, that count will give the number of objects, but when accessing each, you start with 0, so [array count]-1 is the last index.

edited May 26, 2019 at 12:20

Zoe - Save the data dump

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answered Jun 1, 2012 at 12:45

vikingosegundo

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coneybeare · Accepted Answer · 2012-06-01 12:46:21Z

3

Change

 if ((pageNumber < 1) || (pageNumber > photoCount)) return nil;

to

 if ((pageNumber < 0) || (pageNumber >= photoCount)) return nil;

If you have 30 items in your array, the largest accessible index is 29 because the first element is at index 0.

answered Jun 1, 2012 at 12:46

coneybeare

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Comments

mattjgalloway · Accepted Answer · 2012-06-01 12:46:52Z

1

You want:

if ((pageNumber < 0) || (pageNumber >= photoCount)) return nil;

Since it starts at 0 and if you try to get object at index equal to the count, it's reading past the end of the array.

answered Jun 1, 2012 at 12:46

mattjgalloway

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