来自代表的变量不停留

Question

我有一个委托函数“getHeight”，它将父视图控制器的高度发送给另一个视图。

我正在接收高度并将其设置为变量“receivedScreenHeight”

这真的很奇怪，我必须做一些非常愚蠢的事情，但变量“receivedScreenHeight”并没有保持不变。

如果我在收到它后立即打印它会返回667.00但如果我打印它作为一个动作的结果它将返回nil。

这是我的代码部分：

protocol GetMyScreenHeightDelegate {
    func getHeight(height: CGFloat)
}

class pageViewController: UIPageViewController, UIPageViewControllerDataSource, UIPageViewControllerDelegate, GetMyScreenHeightDelegate {


var receivedScreenHeight: CGFloat!


func getHeight(height: CGFloat) {

    print("the height got sent at... \(height)")

    self.receivedScreenHeight = height

    print("the height is set at... \(self.receivedScreenHeight)")

}

func pageViewController(_ pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {
    if (completed && finished) {
        if let currentVC = pageViewController.viewControllers?.last {
            let index = vcArr.index(of: currentVC)

            print("the height remains at... \(self.receivedScreenHeight)")

                //delegate2?.getIndex(index: index!)
            if index == 3 {


                //self.view.frame.size.height = receivedScreenHeight
                self.reloadInputViews()
                self.view.setNeedsLayout()

            }
        }
    }
}

这是控制台：

the height got sent at... 667.0
the height is set at... Optional(667.0)
the height remains at... nil

我无处可见，这有变化，但它突然返回零？

-----编辑-----

来自LandingPageViewController的代码段，用于分配委托和调用函数

override func viewDidLoad() {
    super.viewDidLoad()

    // declare delegate
    self.delegate = pageViewController()

    // call delegate
    let height = self.view.frame.height
    delegate?.getHeight(height: height)

左边的LandingPageController，右边的pageViewController