UICollectionViewCell displaying blank cells when scrolling - ios

Question

I cannot seem to figure out why extra cells are being created and displayed when scrolling or sometimes when I dismiss another view controller to view the cells.
-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
NSInteger tmpIndex = indexPath.row+1; //addd 1 because userDetail is first element
if ([self.model.order[tmpIndex] isKindOfClass:[Products class]])
{
Products *products = [self.model.order objectAtIndex:tmpIndex];
if ([[products display] isEqualToString:kACTIVITY_GRID_CELL_ID])
{
ActivityCollectionViewGridCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:kACTIVITY_GRID_CELL_ID forIndexPath:indexPath];
cell.data = products;
cell.delegate = self;
cell.tag = indexPath.row;
return cell;
}
else
{
ActivityCollectionViewListCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:kACTIVITY_LIST_CELL_ID forIndexPath:indexPath];
cell.data = products;
cell.delegate = self;
cell.tag = indexPath.row;
return cell;
}
}
else
{
OrderHeaders *orderHeaderBaskets = [self.model.order objectAtIndex:tmpIndex];
ActivityCollectionViewListCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:kACTIVITY_LIST_CELL_ID forIndexPath:indexPath];
cell.data = orderHeaderBaskets;
cell.delegate = self;
cell.tag = indexPath.row;
return cell;
}
}
To my understanding it only adds the extra empty cells for this part of the code:
else
{
ActivityCollectionViewListCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:kACTIVITY_LIST_CELL_ID forIndexPath:indexPath];
cell.data = products;
cell.delegate = self;
cell.tag = indexPath.row;
return cell;
}
}
else
{
OrderHeaders *orderHeaderBaskets = [self.model.order objectAtIndex:tmpIndex];
ActivityCollectionViewListCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:kACTIVITY_LIST_CELL_ID forIndexPath:indexPath];
cell.data = orderHeaderBaskets;
cell.delegate = self;
cell.tag = indexPath.row;
return cell;
}
Could this be because I am using dequeueReusableCellWithReuseIdentifier multiple times ? Or is something else causing this ?
Also is there a way to check and remove the extra cells?