NSURLSession dataTaskWithRequest returns nil data - objective-c

Question

I am new to Mac application development and our existing Mac application contains the following line of code
[NSURLConnection sendSynchronousRequest:request returningResonse:response error:Error
A warning message getting displayed as
sendSynchronousRequest is deprecated in macOS 10.11
and suggesting to use [NSURLSession dataTaskWithRequest:completionHandler:]
I have implemented the following code changes to use NSURLSession as suggested but it is returning the value of data as "nil". Can you please suggest what needs to be done in order to get the required data in response?
__block NSError *WSerror;
__block NSURLResponse *WSresponse;
__block NSData *myData;
NSURLSession *session =[NSURLSession sharedSession];
[[session completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
myData = data;
WSresponse =response;
WSerror = error;
}] resume];
NSString *theXml = [[NSString alloc] initWithData:myData encoding:NSUTF8StringEncoding];
return theXml;

Answer 1

The completion handler is asynchronous. You have to do your work inside the completion handler.
The __block declarations are pointless.
NSURLSession *session =[NSURLSession sharedSession];
[[session completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
if (error) {
NSLog(#"%#", error);
} else {
NSString *theXml = [[NSString alloc] initWithData: data encoding:NSUTF8StringEncoding];
// do something with `theXml`
}
}] resume];