UITableView 的使用中，经常出现卡片的使用情况，需要按组切圆角。代码如下：

func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {
        // 获取行数
        let sectionRows = tableView.numberOfRows(inSection: indexPath.section)
        // 设置圆角数值
        let radius = 8.0
        // 创建 CAShapeLayer
        let layer = CAShapeLayer()
        let bounds = cell.bounds
        layer.frame = bounds
        
        
        if indexPath.row == 0, sectionRows == 1 { // 一个为一组,四个圆角
            let path = UIBezierPath.init(roundedRect: bounds, cornerRadius: radius)
            layer.path = path.cgPath
            cell.layer.mask = layer
        } else if indexPath.row == 0 { // 第一个cell,左上,右上切圆角
            let path = UIBezierPath.init(roundedRect: bounds, byRoundingCorners: [.topLeft, .topRight], cornerRadii: .init(width: radius, height: radius))
            layer.path = path.cgPath
            cell.layer.mask = layer
        } else if indexPath.row + 1 == sectionRows { // 最后一个cell,左下,右下切圆角
            let path = UIBezierPath.init(roundedRect: bounds, byRoundingCorners: [.bottomLeft, .bottomRight], cornerRadii: .init(width: radius, height: radius))
            layer.path = path.cgPath
            cell.layer.mask = layer
        }
    }