Code error: UITableViewCell is isn't convertible to Mirrordisposition

Override Func TableView (Tableview:uitableview, Cellforrowatindexpath indexpath:nsindexpath), UITableViewCell {
Let Cellidentifier = "Cellidentifier"
var B_addcell = (Indexpath.row = = Self.listteams.count)
var cell:uitableviewcell! = Tableview.dequeuereusablecellwithidentifier ("UITableViewCell", Forindexpath:indexpath) as? UITableViewCell

if (cell = = nil) {
Cell = UITableViewCell (Style:UITableViewCellStyle.Default, Reuseidentifier:cellidentifier)}//the error of the above code when executing to this position, By adding to the UITableViewCell above! And as plus? , changing the cell to Var will solve the problem.

if (B_addcell = = False) {
Cell.accessorytype = Uitableviewcellaccessorytype.disclosureindicator
Cell.textlabel?. Text = Self.listteams[indexpath.row] as? String

}else{
Self.txtField.frame = CGRectMake (10, 5, 300, 44)
Self.txtField.borderStyle = Uitextborderstyle.none
Self.txtField.placeholder = "Add ..."
Self.txtField.text = ""
Cell.contentView.addSubview (Self.txtfield)}

Configure the cell ...

return cell
}

Code error: UITableViewCell is isn't convertible to Mirrordisposition