Swift3 表视图单元格不会从内存中释放

我希望一切都好 我在表格视图中的单元格有一个问题，当我在表格视图中滚动时，它没有释放。下面是我的代码

class MovieDownloadedTableViewCell: UITableViewCell {

    @IBOutlet weak var movieImageView: UIImageView!
    @IBOutlet weak var movieNameLabel: UILabel!
    @IBOutlet weak var movieEmptyCircleImageView: UIImageView!
    @IBOutlet weak var movieCheckMarkImageView: UIImageView!

    var fetchURL:URL? {
        didSet {
            updateUI()
        }
    }

    func updateUI() {

        movieImageView.image = nil
        movieNameLabel.text = nil
        movieEmptyCircleImageView.isHidden = true
        movieCheckMarkImageView.isHidden = true
        if let fetchURL = fetchURL {
            if fetchURL.pathExtension == "" {
               movieImageView.image = UIImage(named: "folder")
            }else{
               movieImageView.image = UIImage(named: "movie")
            }
            movieNameLabel.text = fetchURL.lastPathComponent

        }// end the if let

    }// end the func updateUI

}// end the class

上面的“我的自定义表格视图”单元格

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

    let cell = tableView.dequeueReusableCell(withIdentifier: "Cell") as? MovieDownloadedTableViewCell

    // defining the cell
    if let cell = cell {
        cell.tintColor = UIColor.white
        cell.fetchURL = operationDocumentDirectoryObject.arrayOfMovieURL?[indexPath.row]

        if isShowToolBar {

        if operationDocumentDirectoryObject?.arrayOfShowAllEmptyCircle?[indexPath.row] == indexPath.row {
            cell.movieEmptyCircleImageView.isHidden = false
            }// end the if

            if operationDocumentDirectoryObject.dictionaryHoldIndexCellForDisplayWhichCellSelected.count > 0 {
                if operationDocumentDirectoryObject.dictionaryHoldIndexCellForDisplayWhichCellSelected[indexPath.row] == indexPath.row {
                    cell.movieEmptyCircleImageView.isHidden = true
                    cell.movieCheckMarkImageView.isHidden = false
                }
            }

        }// end if for the isShowVar

    }// end the creating cell

    return cell!
}

请问我的错误代码在哪里？当我每次从内存中释放滚动时，如何使我的表视图单元格

多谢各位