[SOLVED] How to determine when NSURLSessionTask's request begins?

How to determine when NSURLSessionTask's request begins?

I use NSURLSessionTasks and I'm trying to monitor how long some of my HTTP Requests take, what delegate method (or something else) can I monitor for when the NSURLSessionTask actually makes the initial request? If this were a NSURLConnection inside an NSOperation I'd just start a timer when I start the request but I don't have control over when tasks start.

Solution

Please check NSURLSessionTaskDelegate. It has following delegate callbacks:

URLSession:task:didCompleteWithError:
URLSession:task:didReceiveChallenge:completionHandler:
URLSession:task:didSendBodyData:totalBytesSent:totalBytesExpectedToSend:
URLSession:task:needNewBodyStream:
URLSession:task:willPerformHTTPRedirection:newRequest:completionHandler:

To calculate time interval.

Option 01 [Approximate]:

You should start a timer just after the call to resume method and and calculate when the delegate callback didCompleteWithError is invoked.

self.dataTask = [self.session dataTaskWithRequest:theRequest];
[self.dataTask resume];

NSTimeInterval totalCountdownInterval;
NSDate* startDate = [NSDate date];
NSTimer* timer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(checkCountdown:) userInfo:nil repeats:YES];

Option 02 [If accuracy is desired]:

NSURLSessionTask’s properties are all KVO-compliant.

[self.dataTask addObserver:self forKeyPath:@"someKeyPath" options:NSKeyValueObservingOptionOld context:nil];
[self.dataTask resume];

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context{
  // do some calculation after checking state

   /* 
NSURLSessionTaskStateRunning = 0,                     
    NSURLSessionTaskStateSuspended = 1,
    NSURLSessionTaskStateCanceling = 2,                   
    NSURLSessionTaskStateCompleted = 3, */
}