How to use NSURLSessionDataTask in Swift [closed]

Question

Can someone help me? I can't find a good example for the completion syntax.

var url : NSURL = NSURL.URLWithString("https://itunes.apple.com/search?term=\(searchTerm)&media=software")
var request: NSURLRequest = NSURLRequest(URL:url)
let config = NSURLSessionConfiguration.defaultSessionConfiguration()
let session = NSURLSession.sessionWithConfiguration(config)

NSURLSessionDataTask(session.dataTaskWithRequest(request, completionHandler: ((NSData!, NSURLResponse!, NSError!) -> Void)?)

Answer 1

It's unclear what you're asking, but I noticed that you have a couple of errors in the code:

1. You should create your session using NSURLSession(configuration: config)

2. session.dataTaskWithRequest returns a NSURLSessionDataTask, so there's no need to wrap it inside NSURLSessionDataTask() (a.k.a instantiating a new NSURLSessionDataTask object).

3. The completion handler is a closure and here's how you create that particular clousure:

   {(data : NSData!, response : NSURLResponse!, error : NSError!) in
   
       // your code
   
   }
   

Here's the updated code:

let url = NSURL(string: "https://itunes.apple.com/search?term=\(searchTerm)&media=software")
let request = NSURLRequest(URL: url)
let config = NSURLSessionConfiguration.defaultSessionConfiguration()
let session = NSURLSession(configuration: config)

let task = session.dataTaskWithRequest(request, completionHandler: {(data, response, error) in

    // notice that I can omit the types of data, response and error

    // your code

});

// do whatever you need with the task e.g. run
task.resume()

Answer 2

If you have problems with completion syntax, you can create function for completion before calling dataTaskWithRequest(..) to make it clearer

func handler (data: NSData!, response: NSURLResponse!, error: NSError!) {
            //handle what you need
        }

session.dataTaskWithRequest(request, completionHandler: handler)

Answer 3

You can also use it simply by :-

let url = "api url"

let nsURL = NSURL

let task = NSURLSession.sharedSession().dataTaskWithURL(nsURL) {
(data, response, error) in
   // your condition on success and failure
}

task.resume()

Answer 4

Updated @duemonk's code for Swift 3:

do {
    var request = URLRequest(url: URL(string: "https://www.example.com/api/v1")!, cachePolicy: .useProtocolCachePolicy, timeoutInterval: 10.0)

    let config = URLSessionConfiguration.default
    let session = URLSession(configuration: config)

    let task = session.dataTask(with: request, completionHandler: {(data, response, error) in

         if error != nil {

              print(error!.localizedDescription)

         }

         else {
              print(response)
         }
     })

    task.resume()
}

catch {
// handle the error
}