Kill request

I created a code that request information to webservice, the user typing the word and the app request the information, the webservice return a json. The code worked ok. But I use search bar and a schedule time, when the user stoped to type, the information is requested.

The problem is, if the app request information and the user start typing again the app finish the first request and after request the second information. I need that, when the user request again, the app kill the first request and start second request. Is it possible?

this is the example:

var lastScheduledSearch: NSTimer?
@IBOutlet weak var searchBar: UISearchBar!

..

func searchBar(searchBar: UISearchBar, textDidChange searchText: String) {
        lastScheduledSearch?.invalidate() /
   
        lastScheduledSearch = NSTimer.scheduledTimerWithTimeInterval(1.5, target: self, selector: "startSearching:", userInfo: searchText, repeats: false)
    }

func startSearching(timer: NSTimer) {
        let searchText = timer.userInfo as! String
    
        search(searchText)
    }

func search(searchText: String) {
        let operation = NSBlockOperation()
        operation.addExecutionBlock {
            self.dataController.find(searchText){jsonData, error in
                if let json: AnyObject! = jsonData {
                    self.data = json as! NSArray
                  
                    dispatch_async(dispatch_get_main_queue()) {
                        self.tableView.reloadData()
                    }
                }
            }
          
        }
        currentOperation = operation
        operationQueue.addOperation(currentOperation!)
    }

//class that request json to webservice

func find(search: String,completion: (jsonData: NSArray?, error: NSError?)->Void){
       
        var jsonData:NSArray = []
       
        let post:NSString = "data=\(search)"
       
        let url:NSURL = NSURL(string: links_web.find() as String)!
       
        let postData:NSData = post.dataUsingEncoding(NSUTF8StringEncoding)!
       
        let postLength:NSString = String( postData.length )
       
        let request:NSMutableURLRequest = NSMutableURLRequest(URL: url)
        request.HTTPMethod = "POST"
        request.HTTPBody = postData
        request.setValue(postLength as String, forHTTPHeaderField: "Content-Length")
        request.setValue("application/x-www-form-urlencoded", forHTTPHeaderField: "Content-Type")
        request.setValue("application/json", forHTTPHeaderField: "Accept")
       
       
        let session = NSURLSession.sharedSession()
        let task = session.dataTaskWithRequest(request) {urlData, response, reponseError in
           
            if let receivedData = urlData {
                let res = response as! NSHTTPURLResponse!;
               
                NSLog("Response code: %ld", res.statusCode);
               
                if 200..<300 ~= res.statusCode {
                    do {
                        jsonData = try NSJSONSerialization.JSONObjectWithData(receivedData, options: []) as! NSArray
                        /
                        completion(jsonData: jsonData, error: nil)
                    } catch let error as NSError {
                        
                        completion(jsonData: nil, error: returnedError)
                    }
                } else {
                    
                    completion(jsonData: nil, error: returnedError)
                }
            } else {
                var userInfo: [NSObject: AnyObject] = [
                    "title": "Error!",
                    "message": "Conection fail"
                ]
                if let error = reponseError {
                    userInfo["message"] = error.localizedDescription
                    userInfo["cause"] = error
                }
                let returnedError = NSError(domain: ".", code: 2, userInfo: userInfo)
                /
                completion(jsonData: nil, error: returnedError)
            }
        }
        task.resume()
   
    }