var citiesArray: AnyObject? = nil;

override func viewDidLoad() {
    super.viewDidLoad()

    //loading an array from a file
    var documentList=NSBundle.mainBundle().pathForResource("EuropeanCapitals", ofType:"plist")
    citiesArray = NSArray(contentsOfFile:documentList);

func tableView(tableView: UITableView!, commitEditingStyle editingStyle:        UITableViewCellEditingStyle, forRowAtIndexPath indexPath: NSIndexPath!) {
    if (editingStyle == UITableViewCellEditingStyle.Delete) {
        if let tv=tableView
        {
            citiesArray.removeAtIndex(indexPath!.row) /* Throws Error */
            tv.deleteRowsAtIndexPaths([indexPath], withRowAnimation: .Fade)
        }
    }

if var citiesArr = citiesArray as? Array<AnyObject>{
    citiesArr.removeAtIndex(0)
}