gistfile1.swift

override func shouldPerformSegueWithIdentifier(identifier: String!, sender: AnyObject!) -> Bool {
    
    let needsNavigationController = (splitViewController.traitCollection.horizontalSizeClass == .Regular)
    
    if identifier == "ShowDetail" && needsNavigationController {
        performSegueWithIdentifier("ShowDetailWithNavigationController", sender: sender)
        return false;
    }
    
    return super.shouldPerformSegueWithIdentifier(identifier, sender: sender)
    
}