ios - How to find how many bytes read in NSURLSession in Swift? -

this question has answer here:

• showing file download progress nsurlsessiondatatask 2 answers

note: not duplicate because working in swift, not objective c, please don't mark such.

i have following code download file:

func loadfileasync(url: nsurl, name: string, completion:(path:string, error:nserror!) -> void) {     let documentsurl =  nsfilemanager.defaultmanager().urlsfordirectory(.documentdirectory, indomains: .userdomainmask).first nsurl!     let destinationurl = documentsurl.urlbyappendingpathcomponent(name)     tempdocpath = destinationurl.path!     if nsfilemanager().fileexistsatpath(destinationurl.path!) {         print("file exists [\(destinationurl.path!)]")         completion(path: destinationurl.path!, error:nil)     } else {         let sessionconfig = nsurlsessionconfiguration.defaultsessionconfiguration()         let session = nsurlsession(configuration: sessionconfig, delegate: nil, delegatequeue: nil)         let request = nsmutableurlrequest(url: url)         request.httpmethod = "get"         let task = session.datataskwithrequest(request, completionhandler: { (data: nsdata?, response: nsurlresponse?, error: nserror?) -> void in             if (error == nil) {                 if let response = response as? nshttpurlresponse {                     print("response=\(response)")                     if response.statuscode == 200 {                         if data!.writetourl(destinationurl, atomically: true) {                             print("file saved [\(destinationurl.path!)]")                             completion(path: destinationurl.path!, error:error)                         } else {                             print("error saving file")                             let error = nserror(domain:"error saving file", code:1001, userinfo:nil)                             completion(path: destinationurl.path!, error:error)                         }                     }                 }             }             else {                 print("failure: \(error!.localizeddescription)");                 completion(path: destinationurl.path!, error:error)             }         })         task.resume()     } } 

what need have find bytes read , bytes expected read in order display progress view?

don't use datataskwithrequest(_, completionhandler:) method create data task. instead use datataskwithrequest(_), set delegate, , implement urlsession(_, datatask:,data:) delegate method , monitor size of data blocks receive.