is session.dataTask asynchronous in swift?

Question

I am making requests to my server using the following code:

let configuration = URLSessionConfiguration.default
let session = URLSession(configuration: configuration)
let dataTask = session.dataTask(with: request as URLRequest) { (data, response, error) in
     if error != nil {
          DispatchQueue.main.async(execute: {
              completion(nil, error as NSError?)
          })
          return
     }
     DispatchQueue.main.async(execute: {
          code...
     })    
}
dataTask.resume()

From what I have read this should not block the main thread but it seems to be doing just that. Do I need to call this code after dispatching to another thread? i.e.:

DispatchQueue.global(qos: DispatchQoS.QoSClass.userInitiated).async {

}

Or is dataTask itself requested asynchronously so as not to block the main thread and dispatching this to another thread will be redundant?

Junction

What session are you using? It's is async yes – Lithoid

Something else is definitely blocking it – Kartis

I just edited to include the session with is default configuration – Junction

Answer 1

Yes system given URLSession dataTask is async in nature. Whenever there is a system API call with a completion handler, the API is always async in nature. Concluding, the above implementation is correct. You don't need to put the task in the global queue.

Charla