NSViewAnimation：目标不是视图或窗口

Question

我正在尝试使用动画显示视图，但我得到的只是

> NSViewAnimation target is not view or window ((null))

这很奇怪，因为我很确定我添加的目标是一个视图。我尝试从superview的VC运行动画：

    if let popoverVC = storyboard?.instantiateController(withIdentifier: NSStoryboard.SceneIdentifier(rawValue: "NewEventPopoverViewController")) as? NewEventPopoverViewController {
        self.popoverVC = popoverVC

        let myView = popoverVC.view

        self.view.addSubview(myView)

        let animation = NSViewAnimation.init(viewAnimations: [[.target: myView], [.startFrame: myView.frame.insetBy(dx: 20, dy: 20)], [.endFrame: myView.frame], [.effect: NSViewAnimation.EffectName.fadeIn]])
        animation.duration = TimeInterval(1)
        animation.start()
    }

因为那不起作用，我也尝试从视图的VC本身运行动画：

override func viewDidLoad() {
    super.viewDidLoad()

    let animation = NSViewAnimation.init(viewAnimations: [[.target: self.view], [.startFrame: self.view.frame.insetBy(dx: 20, dy: 20)], [.endFrame: self.view.frame], [.effect: NSViewAnimation.EffectName.fadeIn]])
    animation.duration = TimeInterval(1)
    animation.start()
}

但我只是再次收到相同的错误消息。