如何在iOS中找到TableView中的第n个索引路径?

extension UITableView {
    func indexPath(forIndex index: Int) -> IndexPath? {
        var row = index
        var section = 0
        while section < self.numberOfSections && row >= self.numberOfRows(inSection: section) {
            row -= self.numberOfRows(inSection: section)
            section += 1
        }
        if section < self.numberOfSections {
            return IndexPath(row: row, section: section)
        } else {
            return nil
        }
    }
}

tableView.indexPath(forIndex: 0)

func indexPath(for index: Int) -> IndexPath? {
    var counter = 0
    for sectionIndex in 0..<tableView.numberOfSections {
        for rowIndex in 0..<tableView.numberOfRows(inSection: sectionIndex) {
            if index == counter {
                return IndexPath(row: rowIndex, section: sectionIndex)
            }
            counter += 1
        }
    }
    return nil
}

var neededNumber = 5 - 1 // 5th element

var index:IndexPath?

for sec in 0..<tableView.numberOfSections {

    if neededNumber < tableView.numberOfRows(inSection: sec) {

        index = IndexPath(row: neededNumber, section: sec)

        break
    }
    else
    {
        neededNumber -= tableView.numberOfRows(inSection: sec)
    }

 }

if let myIndex = index {

    print(myIndex)

}