Download a file with NSURLSession in Swift

Question

i have like 2 problems here , first i cant set NSURLSessionDownloadDelegate with a swift project, compiler says

Type 'ViewController' does not conform to protocol 'NSURLSessionDownloadDelegate'

Second problem is i cant find NSURLSession methods to download a simple file

here is the way i use to download the simple file

    var url:NSURL = NSURL.URLWithString(fileURL)
    var request:NSURLRequest = NSURLRequest(URL: url)
    var downloadTask:NSURLSessionDownloadTask = sessionManager.downloadTaskWithRequest(request)
    downloadTask.resume()

and these are the methods i want to make in swift

URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didWriteData:(int64_t)bytesWritten totalBytesWritten:(int64_t)totalBytesWritten totalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite

..

URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didFinishDownloadingToURL:(NSURL *)location

..

URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error

.. if there is a new way to download files with NSURLSession i would like to know , and whats new in NSURLSession in swift

Answer 1

I am at the moment on a project with a background Download Manager, and here are a few things, how I solved that:

if you are using the NSURLSessionDownloadDelegate you need to implement the following methods:

func URLSession(session: NSURLSession!, downloadTask: NSURLSessionDownloadTask!, didFinishDownloadingToURL location: NSURL!) 

func URLSession(session: NSURLSession!, downloadTask: NSURLSessionDownloadTask!, didWriteData bytesWritten: Int64, totalBytesWritten: Int64, totalBytesExpectedToWrite: Int64) 

func URLSession(session: NSURLSession!, downloadTask: NSURLSessionDownloadTask!, didFinishDownloadingToURL location: NSURL!) 

I have done this with this call:

var session:NSURLSession!


    var sessionConfiguration:NSURLSessionConfiguration = NSURLSessionConfiguration.backgroundSessionConfigurationWithIdentifier("com.company")
    sessionConfiguration.HTTPMaximumConnectionsPerHost = 5

    self.session = NSURLSession(configuration: sessionConfiguration, delegate: self, delegateQueue: nil)

// on download

var downloadTask:NSURLSessionDownloadTask = self.session.downloadTaskWithURL(NSURL.URLWithString("urlfromyourfile"))
downloadTask.resume()

// on error:

func URLSession(session: NSURLSession!, task: NSURLSessionTask!, didCompleteWithError error: NSError!) {

    if(error != nil) {

        println("Download completed with error: \(error.localizedDescription)");

    } else {

        println("Download finished successfully");

    }

}

Here you find a good tutorial (i used lots of code from that tutorial and wrote it new with swift)

http://www.appcoda.com/background-transfer-service-ios7/