NSInternalInconsistencyException for UITableView when using UICollectionView? - ios

Question

I was trying to insert items into a collection view with this code:
- (IBAction)addCards:(UIButton *)sender {
int numberOfCardsToAdd = EXTRA_CARDS_NUMBER;
if ([[self.collectionView visibleCells] count] == 0) {
numberOfCardsToAdd = self.startingCardCount;}
// loop through the game model, draw random cards from the deck and assign it to the array
// take into account the "no cards left in deck" case
for (int i = 0; i < numberOfCardsToAdd; i++) {
if (![self.game.deck isEmpty]) {
SetsCard *cardToAdd = (SetsCard *) [self.game.deck drawRandomCard];
if (cardToAdd) [self.game.cards addObject:cardToAdd];
NSIndexPath *newObject = [[NSIndexPath alloc] initWithIndex:[self.game.cards indexOfObject:cardToAdd]];
[self.collectionView insertItemsAtIndexPaths:#[newObject]]; // adding card to view
}
}
[self.collectionView reloadData];
}
and I got this error:
Assertion failure in -[NSIndexPath row], /SourceCache/UIKit_Sim/UIKit-2380.17/UITableViewSupport.m:2680
2013-06-13 09:09:12.443 Improved Matchismo[1206:c07] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Invalid index path for use with UITableView. Index paths passed to table view must contain exactly two indices specifying the section and row. Please use the category on NSIndexPath in UITableView.h if possible.'
*** First throw call stack:
(0x1cb1012 0x10eee7e 0x1cb0e78 0xb84665 0x29eb6c 0x54b14d 0x53fd69 0x53e60e 0x53e646 0x926e 0x1102705 0x362c0 0x36258 0xf7021 0xf757f 0xf66e8 0x65cef 0x65f02 0x43d4a 0x35698 0x1c0cdf9 0x1c0cad0 0x1c26bf5 0x1c26962 0x1c57bb6 0x1c56f44 0x1c56e1b 0x1c0b7e3 0x1c0b668 0x32ffc 0x269d 0x25c5)
libc++abi.dylib: terminate called throwing an exception
which really confuses me because I was adding items to an UICollectionView, not an UITableView, and my app does not use any instance of UITableView at all. Does anyone know why I got this error, and how I can fix it?
Thanks very much in advance!

Answer 1

A collection view works with two-level index paths (section/row) in the same way as
a table view, so you should create the index path
NSIndexPath *newObject = [NSIndexPath indexPathForRow:... inSection:0];
if there is only one section (section 0).
-[NSIndexPath row] is declared in the #interface NSIndexPath (UITableView) category and the error message has probably not been changed when collection views were introduced in iOS 6, so the message "Invalid index path for use with UITableView" is misleading.