展开segue动画错误

Question

我有两个视图控制器，第一个称为“登录视图控制器”，后跟导航控制器，然后是另一个名为“注册视图控制器”的视图控制器。我在网上发现了一篇文章，详细介绍了执行展开segue动画的正确方法，并将此代码放在“Login View Controller”中

 override func segueForUnwinding(to toViewController: UIViewController,
                                from fromViewController: UIViewController,
                                identifier: String?) -> UIStoryboardSegue {
    return UIStoryboardSegue(identifier: identifier, source: fromViewController, destination: toViewController) {
        let fromView = fromViewController.view
        let toView = toViewController.view
        if let containerView = fromView?.superview {
            let initialFrame = fromView?.frame
            var offscreenRect = initialFrame
            offscreenRect?.origin.x -= (initialFrame?.width)!
            toView?.frame = offscreenRect!
            containerView.addSubview(toView!)
            // Being explicit with the types NSTimeInterval and CGFloat are important
            // otherwise the swift compiler will complain
            let duration: TimeInterval = 1.0
            let delay: TimeInterval = 0.0
            let options = UIViewAnimationOptions.curveEaseInOut
            let damping: CGFloat = 0.5
            let velocity: CGFloat = 4.0
            UIView.animate(withDuration: duration, delay: delay, usingSpringWithDamping: damping,
                           initialSpringVelocity: velocity, options: options, animations: {
                            toView?.frame = initialFrame!
            }, completion: { finished in
                toView?.removeFromSuperview()
                if let navController = toViewController.navigationController {
                    navController.popToViewController(toViewController, animated: false)
                }
            })
        }
    }

当我按下“注册视图控制器”内部的后退按钮时，现在发生的是代码成功执行但从视图中删除“登录视图控制器”并停留在“注册视图控制器”上。将“toView？.removeFromSuperview（）”切换为“fromView？.removeFromSuperview（）”后，它成功停留在“登录视图控制器”上，但现在如果按下按钮将我带到“注册视图控制器”，它就会发送我回到“登录视图控制器”本质上创建一个无限循环。