title: Is it possible to detect facebook log in status in iphone's settings?
body: <p>I want to detect that user already log in facebook in iphone's settings?
  I am using Facebook ios sdk 3.1
  In twitter, I can check it by this </p>
  
  <pre><code>[TWTweetComposeViewController canSendTweet]
  </code></pre>
  
  <p>Any suggestions would be appreciate :), thank you very much for your time.</p>