title: disable DeviceOrientationNotification as long as calculation is running
body: <p>my app is doing calculations and showing the results in a graph. When the device is rotating a new <code>UIViewController</code> is generated showing the graph in a landscape-oriented view. Therefore necessary parameters are passed to the new ViewController to create the graph.
  The app is crashing when the device is turned to landscape when the calculation is still running.</p>
  
  <p>Is there a proper way to disable the used <code>DeviceOrientationNotification</code> temporarily?</p>
  
  <pre><code>-(void)calculate
  {
  
  disable DeviceOrientationNotification
  
  ...calculation code here
  
  enable DeviceOrientationNotification again
  
  } 
  </code></pre>
  
  <p>Thanks
  (don't beat me up again, even if the question appears to be stupid)</p>