tableView滑动到底部

- (void)scrollToBottom
{
    NSInteger sectionCount = [self.dataSource numberOfSectionsInTableView:self];
    NSInteger lastSectionRowCount = [self.dataSource tableView:self numberOfRowsInSection:sectionCount-1];
    NSIndexPath *indexPath = [NSIndexPath indexPathForRow:lastSectionRowCount-1 inSection:sectionCount-1];
    [self scrollToRowAtIndexPath:indexPath atScrollPosition:UITableViewRowAnimationTop animated:YES];
}