Ios 来自不同视图控制器的Swift访问约束发现为零

您好，我正在尝试从第二个视图控制器访问我的约束到初始视图控制器，但它总是给出一个错误，我从PageViewController类访问我的约束，以自动调整第二个页面的高度

展开可选值时发现无

Sh_Khan的答案是有效的，但当我想回到pageviewcontroller的第一页时，它并没有回到原来的大小。这是我试过的

 func pageViewController(_ pageViewController: UIPageViewController, willTransitionTo pendingViewControllers: [UIViewController]) {

    let pageContentViewController = pageViewController.viewControllers![0]
    var page = orderedViewControllers.index(of: pageContentViewController)!

   if(page == 1) {     
        let storyboard = UIStoryboard(name: "Main", bundle: nil)
        let vc = storyboard.instantiateViewController(withIdentifier: "MainNeedPage") as! NeedDetailsController

        NeedDetailsController.status.viewstat = "true"
        NeedDetailsController.status.bottomContainerHeightCon = CGFloat(50)
        NeedDetailsController.status.containerHeightCon = CGFloat(30)
        vc.view.layoutIfNeeded()

   } else if(page == 0) {
        let storyboard = UIStoryboard(name: "Main", bundle: nil)
        let vc = storyboard.instantiateViewController(withIdentifier: "MainNeedPage") as! NeedDetailsController;

        NeedDetailsController.status.viewstat = "false"
        NeedDetailsController.status.bottomContainerHeightCon = CGFloat(50)
        NeedDetailsController.status.containerHeightCon = CGFloat(30)
        vc.view.layoutSubviews()
    }
}

在我的初始控制器上

override func viewDidLayoutSubviews() {
    print("statusx: \(NeedDetailsController.status.viewstat)")
    if(NeedDetailsController.status.viewstat == "true"){
        print("statusy: \(NeedDetailsController.status.viewstat)")
        NeedDetailsController.status.viewstat = "false"
        self.bottomContainerHeight.constant = 0
        self.containerHeight.constant = 0
        UIView.animate(withDuration: 1) {
            self.view.layoutIfNeeded()
        }

    } else if(NeedDetailsController.status.viewstat == "false") {
        print("statusz: \(NeedDetailsController.status.viewstat)")
        setupview()
        NeedDetailsController.status.viewstat = "old"
        self.bottomContainerHeight.constant = 50
        self.containerHeight.constant = 30
        UIView.animate(withDuration: 1) {
            self.view.layoutIfNeeded()
        }   
    }   
}

---

无法访问其视图控制器未加载的属性

 vc.bottomContainerHeight.constant = CGFloat(50)
 vc.containerHeight.constant = CGFloat(30)

尝试向该类添加两个变量

  var bottomContainerHeightCon:CGFloat!

  var containerHeightCon:CGFloat!

让他们这样

    let storyboard = UIStoryboard(name: "Main", bundle: nil)
    let vc = storyboard.instantiateViewController(withIdentifier: "MainNeedPage") as! NeedDetailsController;
    vc.bottomContainerHeightCon = CGFloat(50)
    vc.containerHeightCon = CGFloat(30)

和在ViewDidLayoutSubView中

将变量应用于约束

 override func viewDidLayoutSubviews
 {
    if(once){
         once = false
         self.bottomContainerHeight = bottomContainerHeightCon
         self.containerHeight = containerHeightCon
         self.view.layoutIfNeeded()

      }
  }

---

您无法使用

vc

执行任何操作，因为未显示，其所有约束都未初始化。如果您可以帮助我，请查看我的编辑。谢谢。您好，这解决了错误，但我的pageviewcontroller所在的容器视图仍然没有根据给定的高度变量更改其高度。您好，我编辑了我的帖子，遇到了一个新问题。不知道发生了什么事情Git似乎与bundle identifier MainNeedPage完全相同，我正在尝试将其还原为原始大小，例如，我向右滑动底部容器，容器将增大其大小，向左滑动后，底部容器和容器的高度应减小。如果您明白我的意思，请设置NeedDetailsController.status.viewstat=“false”。在第页中为true而不是false=0

 override func viewDidLayoutSubviews
 {
    if(once){
         once = false
         self.bottomContainerHeight = bottomContainerHeightCon
         self.containerHeight = containerHeightCon
         self.view.layoutIfNeeded()

      }
  }