Will [NSURLConnection sendAsynchronousRequest: ...] always send completion block?

Question

Most likely a rather trivial question but will the completion block always be called using [NSURLConnection sendAsynchronousRequest: ...]? OR do I have to implement a timeout timer?

Consider the following where I add a MBProgressView before the call and remove it ONLY in the completion block:

[self showHUDWithTitle:@"Configuring"];
[NSURLConnection sendAsynchronousRequest:request
                                   queue:[[NSOperationQueue alloc] init]
                       completionHandler:^(NSURLResponse *response,
                                           NSData *data,
                                           NSError *error) {

     if ([data length] >0 && error == nil) {
         [self hideHUDWithFlag:YES 
                      andTitle:@"Finished" 
                   andSubtitle:@"(Box was configured)"];

     } else if ([data length] == 0 && error == nil) {
         [self hideHUDWithFlag:NO 
                      andTitle:@"Failed" 
                   andSubtitle:@"(Check box connection)"];
         NSLog(@"Nothing was downloaded.");

     } else if (error != nil) {
        [self hideHUDWithFlag:NO 
                     andTitle:@"Error" 
                  andSubtitle:@"(Check box connection)"];
         NSLog(@"Error = %@", error);
     }
 }];

Answer 1

Yes, the completion handler is always called. If the request fails due to a timeout, the error will be set and data = nil.

A NSURLRequest has a default timeout of 60 seconds, but you can assign a different value to request.timeoutInverval before starting the connection. So there is no need for an extra timer.

Added: In the case of a timeout:

• [error domain] is NSURLErrorDomain, and
• [error code] is NSURLErrorTimedOut,

If you just want to present an error message, you can use [error localizedDescription], which is "The request timed out." in this case. (This may depend on the locale.)

Answer 2

NSURLRequest *request = [[NSURLRequest alloc] initWithURL:url
                                              cachePolicy:NSURLCacheStorageAllowed             
                                          timeoutInterval:20];