SWIFT中切換UIContainerView內的Controller

如下，一個UIContainerView內切換兩個Controller，當點擊登錄的時候UIContainerView的視圖為LoginController，當點擊登記的時候UIContainerView中的視圖為RegisterController

在主視圖內先做兩個按鈕的事件。這個不用說啦。當觸發按鈕事件的時候調用以下代碼就可以。

var newController = self.storyboard?.instantiateViewControllerWithIdentifier("RegisterController") as! RegisterController
            let oldController = childViewControllers.last as! UIViewController
            
            oldController.willMoveToParentViewController(nil)
            addChildViewController(newController)
            newController.view.frame = oldController.view.frame

            //isAnimating = true
            transitionFromViewController(oldController, toViewController: newController, duration: 0.1, options: UIViewAnimationOptions.TransitionNone, animations: nil, completion: { (finished) -> Void in
                    oldController.removeFromParentViewController()
                    newController.didMoveToParentViewController(self)
                    //self.isAnimating = false
            })