       if !switchLocked {
         let currentVc = self.children.last
         let newVc = ColorViewController()
-        newVc.color = currentVc?.view.backgroundColor == .orange ? .blue : .orange
+        newVc.color = currentVc?.view?.backgroundColor == .orange ? .blue : .orange
         self.ex.switchChilds(from: currentVc,
                              to: newVc,
                              in: self.ibExampleView,

import UIKit
import Extra

enum ButtonKind: Int {
  case dashedBorder
  case shadowBorder
  case bottomDivider

    }
    return retValue
  }
}

final class UIKitViewController: UIViewController {
