                     self._drawerConstraint.constant     = constant
                     self._containerView.backgroundColor = UIColor(
                         white: 0
-                        , alpha: self._kContainerViewMaxAlpha
+                        , alpha: self.containerViewMaxAlpha
                     )
                 }
                 self._containerView.layoutIfNeeded()

    @objc public enum DrawerState: Int {
        case Opened, Closed
    }
    
    private let _kContainerViewMaxAlpha  : CGFloat        = 0.2
    
    private let _kDrawerAnimationDuration: NSTimeInterval = 0.25
    
    /**************************************************************************/
    // MARK: - Properties
    /**************************************************************************/
    
    @IBInspectable public var mainSegueIdentifier: String?
    
    @IBInspectable public var drawerSegueIdentifier: String?

            drawerState     = _panDelta < 0 ? .Closed : .Opened
            constant        = min(_drawerConstraint.constant + delta, drawerWidth)
            backGroundAlpha = min(
                containerViewMaxAlpha,
                containerViewMaxAlpha*(abs(constant)/drawerWidth)
            )
        case .Right:
            drawerState     = _panDelta > 0 ? .Closed : .Opened
            constant        = max(_drawerConstraint.constant + delta, -drawerWidth)
            backGroundAlpha = min(
                containerViewMaxAlpha,
                containerViewMaxAlpha*(abs(constant)/drawerWidth)
            )
        }
        
