         
         currentController.removeFromParentViewController()
         
-        self.addChildViewController(controller)
+        addChildViewController(controller)
         controller.beginAppearanceTransition(true, animated:true)
         currentController.beginAppearanceTransition(false, animated:true)
         

        let left:CGFloat = width * horizontal.rawValue
        let top:CGFloat = height * vertical.rawValue
        
        self.addChildViewController(controller)
        
        controller.beginAppearanceTransition(
            true,

    
    func mainController(controller:UIViewController)
    {
        addChildViewController(controller)
        
        guard
            
