NSURLSession dataTaskForRequest:completion: unrecognized selector sent to instance

Question

When trying to create my own session object NSURLSession() and request an url I get an unrecognized selector exception but when I use the shared session NSURLSession.sharedSession() everything works fine. How come?

var url = NSURL(string: "http:/www.google.com")
if url != nil {
    //throws unrecognized selector when dataTaskWithURL is called
    let session=NSURLSession()
    session.dataTaskWithURL(url!)

   //works
    let sharedSession=NSURLSession.sharedSession()
    sharedSession.dataTaskWithURL(url!)
}

Try initializing with configuration. NSURLSession(configuration: NSURLSessionConfiguration.defaultSessionConfiguration()) — MadNik, Oct 02 '15 at 11:13

Arsen · Accepted Answer · 2017-11-10T08:51:49.610

113

You have to init URLSession with a configuration:

URLSession(configuration: .default)

or use shared session

URLSession.shared

edited Nov 10 '17 at 08:51

answered Oct 02 '15 at 11:13

Arsen

10,515
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5

Thanks It works, I assumed that it have used defaultSessionConfiguration by default if I don't pass anything to the constructor – Alexey Oct 02 '15 at 11:16
1

For Swift 3 the syntax is now: URLSession(configuration: URLSessionConfiguration.default) – David Hunt Sep 01 '16 at 00:31

pierre23 · Answer 2 · 2018-03-04T20:32:56.063

5

In SWIFT 3.0 and up:

        URLSession.shared.dataTask(with: url, completionHandler:
        {
            (data, response, error) in

            //Your code
        }).resume()

edited Mar 04 '18 at 20:32

answered Oct 17 '16 at 15:44

pierre23

3,718
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score 2 · Answer 3 · answered Oct 02 '15 at 11:15

Aside from the shared session NSURLSession must be initialized with one of these two methods

init(configuration configuration: NSURLSessionConfiguration)


init(configuration configuration: NSURLSessionConfiguration,
               delegate delegate: NSURLSessionDelegate?,
             delegateQueue queue: NSOperationQueue?)

score 1 · Answer 4 · answered May 02 '17 at 14:41

1

Do the initialization while declaration :-

var session = URLSession(configuration: .default)

answered May 02 '17 at 14:41

Jay Mehta

1,271
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18

NSURLSession dataTaskForRequest:completion: unrecognized selector sent to instance

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