Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[__NSArrayM objectAtIndex:]: index 0 beyond bounds for empty array

Question

So I have a UITableView, and the app crashes with this error every time that the array does not have any items in it. What is strange is that I have another table that does not crash when it has zero objects in the array, and I am using almost identical code for each. Here is what I have:

@implementation FindFBFriendsViewController {
    NSMutableArray *friends;
}

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    UserFBFriends *fbFriends = [UserFBFriends sharedInstance];
    NSLog(@"Hell0 from the fbfriends view, array is %@", fbFriends.userFriends);
    friends = [[NSMutableArray alloc] initWithArray:fbFriends.userFriends];

    IndFBFriend *testFriend = [friends objectAtIndex:0];
    NSLog(@"USER Friends:    %@", testFriend.fullName);
}

-(void)viewWillAppear:(BOOL)animated {
    [self.fbTableView reloadData];
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    return [friends count];
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
     FBFriendCell *cell = [tableView dequeueReusableCellWithIdentifier:@"friendCell" forIndexPath:indexPath];

    if (cell == nil) {
        NSArray *nib = [[NSBundle mainBundle] loadNibNamed:@"FBFriendCell" owner:self options:nil];
        cell = [nib objectAtIndex:0];
    }

    IndFBFriend *indexRowFriend = [friends objectAtIndex:indexPath.row];
    [cell updateCellWithName:indexRowFriend.fullName profilePicture:indexRowFriend.profPic personFBId:indexRowFriend.fbId];

    cell.backgroundColor = [UIColor clearColor];
    return cell;
}

Here is the stack:

Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[__NSArrayM objectAtIndex:]: index 0 beyond bounds for empty array'
*** First throw call stack:
(
    0   CoreFoundation                      0x0000000106213d85 __exceptionPreprocess + 165
    1   libobjc.A.dylib                     0x000000010597adeb objc_exception_throw + 48
    2   CoreFoundation                      0x00000001060f1804 -[__NSArrayM objectAtIndex:] + 212
    3   gif-wrap                            0x000000010338dd24 -[FindFBFriendsViewController viewDidLoad] + 340
    4   UIKit                               0x000000010421b984 -[UIViewController loadViewIfRequired] + 1198
    5   UIKit                               0x000000010422193b -[UIViewController __viewWillAppear:] + 120
    6   UIKit                               0x0000000104251750 -[UINavigationController _startCustomTransition:] + 1203
    7   UIKit                               0x0000000104261b9b -[UINavigationController _startDeferredTransitionIfNeeded:] + 712
    8   UIKit                               0x0000000104262d0b -[UINavigationController __viewWillLayoutSubviews] + 57
    9   UIKit                               0x0000000104411503 -[UILayoutContainerView layoutSubviews] + 248
    10  UIKit                               0x000000010413b980 -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 703
    11  QuartzCore                          0x0000000109754c00 -[CALayer layoutSublayers] + 146
    12  QuartzCore                          0x000000010974908e _ZN2CA5Layer16layout_if_neededEPNS_11TransactionE + 366
    13  QuartzCore                          0x0000000109748f0c _ZN2CA5Layer28layout_and_display_if_neededEPNS_11TransactionE + 24
    14  QuartzCore                          0x000000010973d3c9 _ZN2CA7Context18commit_transactionEPNS_11TransactionE + 277
    15  QuartzCore                          0x000000010976b086 _ZN2CA11Transaction6commitEv + 486
    16  UIKit                               0x000000010407b72e _UIApplicationHandleEventQueue + 7135
    17  CoreFoundation                      0x0000000106139301 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 17
    18  CoreFoundation                      0x000000010612f22c __CFRunLoopDoSources0 + 556
    19  CoreFoundation                      0x000000010612e6e3 __CFRunLoopRun + 867
    20  CoreFoundation                      0x000000010612e0f8 CFRunLoopRunSpecific + 488
    21  GraphicsServices                    0x0000000109204ad2 GSEventRunModal + 161
    22  UIKit                               0x0000000104080f09 UIApplicationMain + 171
    23  gif-wrap                            0x00000001033922ef main + 111
    24  libdyld.dylib                       0x000000010752892d start + 1
    25  ???                                 0x0000000000000001 0x0 + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException

Does anybody know how I can solve this issue?

Answer 1

You say yourself that this happens when the friends array is empty. What do you expect to see when you run the following:

IndFBFriend *testFriend = [friends objectAtIndex:0];

-[NSArray objectAtIndex:] throws an exception when you access an index that does not exist; when friends is empty, that's what you see. Index 0 is invalid for an empty array.

You haven't posted your other code, but I'm guessing that your other code does not contain a line like this, so it does not crash.