iOS:将 scrollPosition 设置为 `UITableViewScrollPositionMiddle` 它没有滚动到正确的位置

Question

这是我的代码:

 if (![self.cityLabel.text isEqualToString:@""] && dataOfCity.count != 0) {
        for (int i = 0; i < dataOfCity.count; i ++) {

            if ([dataOfCity[i] isEqualToString:self.cityLabel.text]) {

                NSIndexPath *indexPath = [NSIndexPath indexPathForRow:i inSection:0];
                [_tab_city selectRowAtIndexPath:indexPath animated:YES scrollPosition:UITableViewScrollPositionMiddle];
            }
        }

    }

结果是不在下面tableView中间的图片:

Answer 1

I think I understand what happens: 
the table view is already performing another animation and the scrollToRowAtIndexPath is ignored. 
Wrapping the method in CATransaction block works for me (swift code):

    CATransaction.begin()

    tableView.beginUpdates()
    tableView.scrollToRowAtIndexPath(cell.indexPath, atScrollPosition: .Middle, animated: true)
    tableView.endUpdates()

    CATransaction.commit()

    Another solution that worked for me was using performSelectorWithDelay, with the delay being long enough for other animations on the table view to finish.