URLSessionDelegate methods not called - swift

Question

Firstly, I already checked similar existing questions, and none of the answers apply.
NSURLSession delegates not called
URLSessionDelegate Function Not Being Called
I am trying to download a file using URLSessionDownloadTask, like so
class MyNetworkManager : NSObject
{
static let instance = MyNetworkManager()
var downloadSession : URLSession?
init()
{
super.init()
let downloadConfiguration = URLSessionConfiguration.default
downloadSession = URLSession(configuration: downloadConfiguration, delegate: self, delegateQueue: nil)
}
func download(_ url : URL)
{
var urlRequest = URLRequest(url: url)
urlRequest.httpMethod = "GET"
let downloadTask = downloadSession?.downloadTask(with: urlRequest)
downloadTask?.resume()
}
}
extension MyNetworkManager : URLSessionDelegate
{
func urlSession(_ session: URLSession,
downloadTask: URLSessionDownloadTask,
didWriteData bytesWritten: Int64,
totalBytesWritten: Int64,
totalBytesExpectedToWrite: Int64)
{
//
}
func urlSession(_ session: URLSession,
downloadTask: URLSessionDownloadTask,
didFinishDownloadingTo location: URL)
{
//
}
func urlSession(_ session: URLSession,
task: URLSessionTask,
didCompleteWithError error: Error?)
{
//
}
}
However, no URLSessionDelegate methods are called.
Normally, delegate methods are not called if you create a task with completion handler - that is not the case, I'm only using URLRequest as parameter when creating a task.
Session's delegate is properly set, and after calling downloadTask?.resume() its state property is running
MyNetworkManager is a singleton, I'm using it like so
MyNetworkManager.instance.download(someURL)
so an instance is definitely retained.
Am I missing something here?

Answer 1

You must conform to the relevant protocols, e.g.:
extension MyNetworkManager: URLSessionDelegate {
// this is intentionally blank
// obviously, if you implement any delegate methods for this protocol, put them here
}
extension MyNetworkManager: URLSessionDownloadDelegate {
func urlSession(_ session: URLSession,
downloadTask: URLSessionDownloadTask,
didWriteData bytesWritten: Int64,
totalBytesWritten: Int64,
totalBytesExpectedToWrite: Int64) {
print(#function)
}
func urlSession(_ session: URLSession,
downloadTask: URLSessionDownloadTask,
didFinishDownloadingTo location: URL) {
print(#function)
}
}
extension MyNetworkManager: URLSessionTaskDelegate {
func urlSession(_ session: URLSession,
task: URLSessionTask,
didCompleteWithError error: Error?) {
print(#function, error ?? "No error")
}
}
If you don’t conform to URLSessionDownloadDelegate, it won’t call URLSessionDownloadDelegate methods.