title: CoreData - check if object exists in database
body: <p>I have viewController with table view and FetchResultsController. ViewController downloads data from web and then save it to CoreData. Downloading happens every launch. I need someway to compare info that I downloaded from web and only the save it to CoreData</p>
  
  <p>How can I do this ? </p>
  
  <p>I had an idea of fetching all objects by <code>fetchedResultsController.performFetch()</code> and then assigning them to array, but I dont understand how to iterate over that array (it us [AnyObject])</p>
  
  <p>Maybe there are more easy ways ?</p>