1)如何返回screenHeight / cellCount作为第一种方法的CGFLoat？

2)如何在第二种方法中使用等价的ObjC的MIN()和MAX()？

func tableView(tableView: UITableView!,heightForRowAtIndexPath indexPath: NSIndexPath!) -> CGFloat {
    var cellCount = Int(self.tableView.numberOfRowsInSection(indexPath.section))

    return screenHeight / cellCount as CGFloat
}

// #pragma mark - UIScrollViewDelegate

func scrollViewDidScroll(scrollView: UIScrollView) {
    let height = CGFloat(scrollView.bounds.size.height)
    let position = CGFloat(MAX(scrollView.contentOffset.y,0.0))

    let percent = CGFloat(MIN(position / height,1.0))
    blurredImageView.alpha = percent
}