试图在上一个视图控制器上更新UI时崩溃
好吧，我有视图控制器A呈现查看控制器B，就像这样...
@IBAction func presentView(_ sender: Any) {
let storyBoard : UIStoryboard = UIStoryboard(name: "main", bundle:nil)
let vc = storyBoard.instantiateViewController(withIdentifier: "Popout") as! PopoutWindow
vc.modalTransitionStyle = .coverVertical
vc.modalPresentationStyle = .overFullScreen
self.present(vc, animated:true, completion:nil)
}
完成视图控制器B时，我会像这样将其视为...
let vc = WellnessPlanEnrollmentController()
self.dismiss(animated: true, completion: {
vc.refreshView()
})
然后我所呼叫的功能正在尝试使用该功能更新我的UI来自View ControllerB的新数据B。但是，当我重新加载第一个视图时，我会遇到一个奇怪的崩溃，说我要更新的标签是无。
func refreshView() {
DispatchQueue.main.async {
self._petNameLabel.text = self.object.name
// crashes here because my label is nil???????
}
}
错误：firstViewController.swift：128：致命错误：意外发现的同时暗中解开可选值
我觉得这是因为当我调用函数时，视图不在焦点当然。
Alright I have view controller A that presents view controller B like so...
@IBAction func presentView(_ sender: Any) {
let storyBoard : UIStoryboard = UIStoryboard(name: "main", bundle:nil)
let vc = storyBoard.instantiateViewController(withIdentifier: "Popout") as! PopoutWindow
vc.modalTransitionStyle = .coverVertical
vc.modalPresentationStyle = .overFullScreen
self.present(vc, animated:true, completion:nil)
}
When I'm done with view controller B, I dismiss it like so...
let vc = WellnessPlanEnrollmentController()
self.dismiss(animated: true, completion: {
vc.refreshView()
})
And then the function I'm calling is attempting to update my UI with the new data from view controller B. However, when I reload the first view, I get a weird crash saying that my label I'm trying to update is nil.
func refreshView() {
DispatchQueue.main.async {
self._petNameLabel.text = self.object.name
// crashes here because my label is nil???????
}
}
Error: FirstViewController.swift:128: Fatal error: Unexpectedly found nil while implicitly unwrapping an Optional value
I feel like it's because the view is not in focus when I'm calling the function but I'm not sure.
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这是失败的，因为您创建了
wellnessplanenrollmentController的新实例。此实例没有连接到任何故事板或查看，因此其所有插座都是零。可能的解决方案：
在您的控制器
b中创建一个委托，然后在介绍之前将其分配并在解雇后调用。This is failing because you create a new instance of
WellnessPlanEnrollmentController. This instance is not connected to any Storyboard or View so all of its outlets are nil.Possible solution:
Create a delegate in your controller
Band assign it before presenting and call it after dismiss.