peek.m

- (UIViewController *)previewingContext:(id<UIViewControllerPreviewing>)previewingContext         
              viewControllerForLocation:(CGPoint)location 
{
    // query the collectionView for index corresponting to the touch location
    NSIndexPath *indexPath = [self.collectionView indexPathForItemAtPoint:location];

    // just in case
    if (!indexPath) { return nil; }

    // get the data object corresponding to the pressed cell
    HNMemberLite *lite = self.memberService.members[indexPath.row];

    // filter out non member objects (aka ads)
    if (![lite isKindOfClass:[HNMemberLite class]]) { return nil; }

    // set the source rectangle for proper animation
    CGRect rect = [self.collectionView layoutAttributesForItemAtIndexPath:indexPath].frame;
    [previewingContext setSourceRect:rect];

    // instantiate the peek controller and return it
    UIViewController *controller = [[HNTMemberPeekViewController alloc] initWithMember:lite];

    return controller;
}