NSURLSession dataTaskForRequest:completion: unrecognized selector sent to instance
You have to init URLSession with a configuration:
URLSession(configuration: .default)or use shared session
URLSession.shared
In SWIFT 3.0 and up:
URLSession.shared.dataTask(with: url, completionHandler: { (data, response, error) in //Your code }).resume()
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?)