title: Optional type 'Bool' cannot be used as a boolean; test for '!= nil' instead
body: <pre><code> override func prepareForSegue(segue: UIStoryboardSegue?, sender: AnyObject?) {
            if (segue &amp;&amp; segue!.identifier == "showDetail"){  //this line has error
              var selectedIndexPath : NSIndexPath = self.tableView.indexPathForSelectedRow()
              var detailViewController : DetailViewController = segue!.destinationViewController as DetailViewController
              detailViewController.toDoData = toDoItems.objectAtIndex(selectedIndexPath.row) as NSDictionary
          }
  </code></pre>
  
  <p>I am very newby, it may be very simple error, but I need well explained answer.
  I have Xcode error </p>
  
  <blockquote>
    <p>Optional type 'Bool' cannot be used as a boolean; test for '!= nil'
    instead</p>
  </blockquote>
  
  <p>for the second line <code>segue &amp;&amp; segue!.identifier</code>.</p>
  
  <p>I am watching youtube video to follow steps for the to-do list.</p>