Creating a button to scroll UICollectionView

Question

I have a button connected from storyboard that I want to scroll my horizontally scrolling collection view one item to the right when pressed. Here is the code I came up with:

- (IBAction)rightButton:(id)sender {
    NSIndexPath *indexPath = [self.collectionView indexPathsForSelectedItems];
    NSIndexPath* newIndexPath = [NSIndexPath indexPathForRow:indexPath.row+1 inSection:indexPath.section];


    [self.collectionView scrollToItemAtIndexPath:newIndexPath
                            atScrollPosition:UICollectionViewScrollPositionCenteredHorizontally
                                    animated:YES];

}

However, this is creating a crash, with the error

 -[__NSArrayI row]: unrecognized selector sent to instance 0x178232540
 *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSArrayI row]: unrecognized selector sent to instance 0x178232540'

I suspect the problem is that this code is more for a TableView and it doesn't like the section park in there.

Can someone help me out with this and figure out why I get an error? Is there a better way to do this?

Thanks

Answer 1

The indexPathsForSelectedItems method name has an extra s in it, Paths not Path, which indicates that it returns an NSArray of index paths, not a single index path. Hence the solution is to change these lines

NSIndexPath *indexPath = [self.collectionView indexPathsForSelectedItems];
NSIndexPath* newIndexPath = [NSIndexPath indexPathForRow:indexPath.row+1 inSection:indexPath.section];

to this

NSIndexPath *newIndexPath = [NSIndexPath indexPathForRow:0 inSection:0];

NSArray *indexPaths = [self.collectionView indexPathsForSelectedItems];
if ( indexPaths.count > 0 )
{
    NSIndexPath *oldIndexPath = indexPaths[0];
    NSInteger oldRow = oldIndexPath.row;
    newIndexPath = [NSIndexPath indexPathForRow:oldRow + 1 inSection:oldIndexPath.section];
}