title: Use NSMutableDictionary writeToFile method that contains CLPlacemark objects
body: <p>I have a <code>NSMutableDictionary</code> that contains some objects..</p>
  
  <p>Between these objects I have also a <code>CLPlacemark</code>.</p>
  
  <p>I would to use the method <code>writeToFile:pathFile atomically:YES</code> to salve on file but if the dictionary contains the CLPlacemark the operation fails..</p>
  
  <p>How can I use the method to save if I also objects of that type? </p>
  
  <p>One first idea was to convert the <code>CLPlacemark</code> to <code>NSData</code>... there are other solutions?</p>