"Authentication Required" with NSURLSession. User/Key correct - ios

Question

I'm new to Objective-C and am struggling to get the following code to work properly. Logging out dataString is telling me that the API is returning an "Authentication Required" message. When I put the resulting URL into a browser, however, the information I want is returned correctly. What am I missing? Is NSURLSession doing something to change the request?
- (void)fetchWX
{
NSString *requestString = [NSString stringWithFormat:#"http://%#:%##flightxml.flightaware.com/json/FlightXML2/Metar?airport=%#", FLIGHTAWARE_USERNAME, FLIGHTAWARE_API_KEY, _airport];
NSURL *url = [NSURL URLWithString:requestString];
NSURLRequest *req = [NSURLRequest requestWithURL:url];
NSURLSessionDataTask *dataTask = [self.urlSession dataTaskWithRequest:req completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
NSString *dataString = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
NSDictionary *jsonObject = [NSJSONSerialization JSONObjectWithData:data options:0 error:nil];
NSLog(#"%#", dataString);
}];
[dataTask resume];
}
There's another method in my app with a similar structure that's working properly, and FlightAware's synchronous example using NSURLConnection also works fine. Just can't seem to use NSURLSession.

Answer 1

NSURLSessionConfiguration *config = [NSURLSessionConfiguration ephemeralSessionConfiguration];
config.HTTPAdditionalHeaders = #{ #"Accept":#"application/json"};
NSURLSession *urlSession = [NSURLSession sessionWithConfiguration:config delegate:self delegateQueue:nil];
NSURL *url = [NSURL URLWithString:path];
NSURLRequest *req = [NSURLRequest requestWithURL:url];
NSURLSessionDataTask *dataTask = [urlSession dataTaskWithRequest:req completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
NSDictionary *jsonObject = [NSJSONSerialization JSONObjectWithData:data options:0 error:nil];
NSLog(#"jsonObject is %#",jsonObject);
}];
and add this delegate method, which will be called once to resolve the authentication challenge.
-(void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didReceiveChallenge:(NSURLAuthenticationChallenge *)challenge completionHandler:(void (^)(NSURLSessionAuthChallengeDisposition, NSURLCredential *))completionHandler {
NSString *user = #"YourUserName";
NSString *password = #"YourKey";
NSLog(#"didReceiveChallenge");
// should prompt for a password in a real app but we will hard code this baby
NSURLCredential *secretHandshake = [NSURLCredential credentialWithUser:user password:password persistence:NSURLCredentialPersistenceForSession];
// use block
completionHandler(NSURLSessionAuthChallengeUseCredential,secretHandshake);
}
I have tested it and it worked.