title: getting [NSURL cachePolicy]: unrecognized selector sent to instance during downloading an image,AFNetworking
body: <p>My purpose is trying to get the size of the downloaded image via the successful block like below:</p>
  
  <pre><code>[imageView setImageWithURLRequest:[NSURL URLWithString:((ObjectA*)obj[indexPath.row]).imageUrl]
                  placeholderImage:nil
                           success:^(NSURLRequest *request, NSHTTPURLResponse *response, UIImage *image) {
                              CGFloat imageHeight = image.size.height;
                              CGFloat imageWidth = image.size.width;
                              NSLog(@"width of image is %f",imageWidth);
                              NSLog(@"height of image is %f",imageHeight);
                          }
                          failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error) {
                              ;
                          }  ];
  </code></pre>
  
  <p>However, I am getting a crash with shown error like below :</p>
  
  <pre><code> *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSURL cachePolicy]: unrecognized selector sent to instance 0x1edb9e70'
  </code></pre>
  
  <p>Does anybody know the reason for this error. Please help if you have any ideas</p>