Download JSON in background thread

AFNetworking is an open source networking library for iOS and Mac OS X, making it easy to downloading JSON in a background thread::

NSURL *url = [NSURL URLWithString:@"http://someURL"];
NSURLRequest *request = [NSURLRequest requestWithURL:url];
AFJSONRequestOperation *operation = [AFJSONRequestOperation JSONRequestOperationWithRequest:request 
  success:^(NSURLRequest *request, NSHTTPURLResponse *response, id JSON) {
    NSLog(@"JSON data: %@", JSON);
} failure:nil];
 
[operation start];

AFNetworking on github