didReceive Challenge Authentication Method Not Called - ios

Question

Following is my code . I am trying to use didReceive challenge method for authentication. Apple documents says that If a session task requires authentication, and there are no valid credentials available, then 'didReceive challenge' method is called. but in this case it is not being called. Any advice will be appreciated. Thanks :)
func getServerResponse(){
var request=URLRequest(url: URL(string: "http://dev.example.com/Api/Account")!)
let configuration=URLSessionConfiguration.default
request.httpMethod="GET"
let task=URLSession.init(configuration: configuration).dataTask(with: request, completionHandler: {(data,response,error) -> Void in
do {
if let jsonResult = try JSONSerialization.jsonObject(with: data!, options: []) as? NSDictionary {
print("Result-->\(jsonResult)")
print((response as! HTTPURLResponse).statusCode)
}
} catch let error as NSError {
print(error.localizedDescription)
}
})
task.resume()
}
func urlSession(_ session: URLSession, task: URLSessionTask, didReceive challenge: URLAuthenticationChallenge, completionHandler: #escaping (URLSession.AuthChallengeDisposition, URLCredential?) -> Void) {
let crdential = URLCredential.init(user:"userName", password: "password", persistence: URLCredential.Persistence.none)
completionHandler(URLSession.AuthChallengeDisposition.useCredential, crdential)
}

Answer 1

The delegate is not being called because you have not set the delegate in the first place......
Use this method:
let task = URLSession(configuration: configuration, delegate: self, delegateQueue: nil)
Also, set the URLSessionDataDelegate and conform the protocol:
func urlSession(_ session: URLSession, dataTask: URLSessionDataTask, didReceive response: URLResponse, completionHandler: #escaping (URLSession.ResponseDisposition) -> Swift.Void)
Instead of using dataTask with completion handler because when you use that method it does not call any of the delegate methods.

Answer 2

Would like to supplement the existing answer by mentioning that Apple provide an excellent article on this. The article includes sample code. See Handling an Authentication Challenge.
Also, to mention, Apple - in both in their docs and developer forums - strongly recommend the delegate approach to handling basic authentication challenges. However! it’s worth noting that not all REST API’s issue a challenge. For example, some API’s provide a default level of access to anonymous users. They do not issue the challenge.
So, having implemented delegates correctly, if the callbacks are not executing, it’s worth checking the REST API documents on basic auth.
It maybe that there is no choice but to delegate handling and pass the appropriate headers instead:
var request = URLRequest(url: url)
request.setValue(basicAuthHeader, forHTTPHeaderField: "Authorization”)
and to provide the headers:
// Set the security header
private var credentials: String {
return "\(username):\(password)"
}
private var basicAuthHeader: String {
let data = credentials.data(using: String.Encoding.utf8)!
let encoded = data.base64EncodedString()
return "Basic \(encoded)"
}