NSURLSession delegate vs. completionHandler - ios

Question

I've always used completion handlers. With NSURLConnection and now with NSURLSession. It's led to my code being really untidy, especially I have request within request within request.
I wanted to try using delegates in NSURLSession to implement something I've done untidily with NSURLConnection.
So I created a NSURLSession, and created a dataTask:
NSURLSessionDataTask *dataTask = [overallSession dataTaskWithURL:url
completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
if(error == nil)
{
NSString * text = [[NSString alloc] initWithData: data encoding: NSUTF8StringEncoding];
NSLog(#"Data = %#",text);
}
}];
[dataTask resume];
Right now I have a completionHandler for the response, how would I switch to delegates to manage the response and data? And can I add another dataTask from the delegate of this one? Using the cookies that this dataTask created and placed into the session?

Answer 1

If you want to add a custom delegate class, you need to implement the NSURLSessionDataDelegate and NSURLSessionTaskDelegate protocols at the minimum.
With the methods:
NSURLSessionDataDelegate - get continuous status of your request
- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveResponse:(NSURLResponse *)response
completionHandler:(void (^)(NSURLSessionResponseDisposition disposition))completionHandler {
receivedData=nil; receivedData=[[NSMutableData alloc] init];
[receivedData setLength:0];
completionHandler(NSURLSessionResponseAllow);
}
NSURLSessionDataDelegate
-(void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask
didReceiveData:(NSData *)data {
[receivedData appendData:data];
}
NSURLSessionTaskDelegate
- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task
didCompleteWithError:(NSError *)error {
if (error) {
// Handle error
}
else {
NSDictionary* response=(NSDictionary*)[NSJSONSerialization JSONObjectWithData:receivedData options:kNilOptions error:&tempError];
// perform operations for the NSDictionary response
}
If you want to separate the delegate code (middle layer) from your calling class (generally its good practice to have separate class/layer for network calls), the delegate of NSURLSession has to be :-
NSURLSession *session=[NSURLSession sessionWithConfiguration:sessionConfig delegate:myCustomDelegateClass delegateQueue:nil];
Ref Links:
NSURLSession Class Reference
iOS NSURLSession Example (HTTP GET, POST, Background Downlads )
From NSURLConnection to NSURLSession