title: User not logged in error in Facebook SDK iOS
body: <p>How can I fix this error in my program? Using Facebook SDK.</p>
  
  <pre><code>Error Domain=facebookErrDomain Code=10000 "The operation couldn’t be completed. (facebookErrDomain error 10000.)" UserInfo=0x5da9b10 {error=&lt;CFBasicHash 0x5db09a0 [0x1087400]&gt;{type = mutable dict, count = 2,
  entries =&gt;
      2 : &lt;CFString 0x5db7920 [0x1087400]&gt;{contents = "type"} = &lt;CFString 0x5d35420 [0x1087400]&gt;{contents = "OAuthException"}
      3 : &lt;CFString 0x5d34970 [0x1087400]&gt;{contents = "message"} = &lt;CFString 0x5da96b0 [0x1087400]&gt;{contents = "Error validating access token: The session is invalid because the user logged out."}
  }
  }
  </code></pre>