title: NSData dataWithContentsOfURL
body: <p>I have this method for button click (download). The problem is that it is terminating due to an exception:</p>
  
  <pre>
  [Session started at 2011-03-14 13:06:45 +0530.]
  2011-03-14 13:06:45.710 XML[7079:20b] *** Terminating app due to uncaught exception 'NSInvalidArgumentException',
  reason: '*** -[NSCFString isFileURL]: unrecognized selector sent to instance 0x62b8'
  </pre>
  
  <pre><code>-(IBAction) download
  {
      UIImage *image = [UIImage imageWithData: [NSData dataWithContentsOfURL:@"http://ws.cdyne.com/WeatherWS/Images/thunderstorms.gif"]];
      [image release];
  }
  </code></pre>
  
  <p>What is the problem?</p>