如何從NSURLSession.sharedSession().dataTaskWithRequesclass PostFOrData {     let url = NSURL( string: "http://210.61.209.194:8088/SmarttvWebServiceTopmsoApi/GetReadlist")     var picUrl = NSURL(string : "http://210.61.209.194:8088/SmarttvMedia/img/epi00001.png")     var responseString : NSString = ""     func forData() -> NSString {         let request = NSMutableURLRequest( URL: url!)         request.HTTPMethod = "POST"         var s : NSString = ""         let postString : String = "uid=59"         request.HTTPBody = postString.dataUsingEncoding(NSUTF8StringEncoding)         let task = NSURLSession.sharedSession().dataTaskWithRequest(request) {             data, response, error in             if error != nil {                 println("error=\(error)")                 return             } else {                 println("response = \(response!)")                 self.responseString = NSString(data: data, encoding: NSUTF8StringEncoding)!                 println("responseString = \(self.responseString)")             }         }         // I want to return NSString here, but I always get nothing         return self.responseString    }}有人知道如何從任務中獲取數據嗎？