获取cell (tableviewcell、collectionviewcell)
NSIndexPath *indexPath = [NSIndexPath indexPathForRow:0 inSection:0];
ACEExpandableTextCell * cell = (ACEExpandableTextCell *)[self.tableView cellForRowAtIndexPath:indexPath];
NSIndexPath *indexPath = [NSIndexPath indexPathForItem:0 inSection:0];
TitleViewCell * cell = (TitleViewCell *)[self.collectionView cellForItemAtIndexPath:indexPath];//即为要得到的cell