ios – NSIndexPath和IndexPath在Swift 3.0中

我最近将我的代码转换为Swift 3.0.我的集合视图和表视图数据源方法现在在其方法签名中包含IndexPath而不是NSIndexPath.但是仍然在方法定义中,将IndexPath类型转换为NSIndexPath.即

func collectionView(_ collectionView: UICollectionView,cellForItemAt indexPath: IndexPath) -> UICollectionViewCell
    {
        let cell : NNAmenitiesOrFurnishingCollectionViewCell = self.amenitiesOrFurnishingCollectionView.dequeueReusableCell(withReuseIdentifier: "NNAmenitiesOrFurnishingCollectionViewCell",for: indexPath) as! NNAmenitiesOrFurnishingCollectionViewCell
        cell.facilityImageName = self.facilityArray[(indexPath as NSIndexPath).row].imageName
        cell.facilityLabelString = self.facilityArray[(indexPath as NSIndexPath).row].labelText
        return cell
    }

任何人都可以告诉我为什么indexPath被转换为NSIndexPath.

/// The section of this index path,when used with `UITableView`.
///
/// - precondition: The index path must have exactly two elements.
public var section: Int

/// The row of this index path,when used with `UITableView`.
///
/// - precondition: The index path must have exactly two elements.
public var row: Int

cell.facilityImageName = self.facilityArray[indexPath.row].imageName
    cell.facilityLabelString = self.facilityArray[indexPath.row].labelText