xcode 无法转换“UINavigationController”类型的值
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Could not cast value of type 'UINavigationController'
提问by Semih Yagcioglu
I am implementing a search interface for my application, so basically I will pass the search keyword from one ViewController to another ViewController.
我正在为我的应用程序实现一个搜索界面，所以基本上我会将搜索关键字从一个 ViewController 传递到另一个 ViewController。
I have done this type of parameter passing several times but something seems strange this time. The destination ViewController is embedded in a Navigation Controller.
我已经多次传递这种类型的参数，但这次似乎有些奇怪。目标 ViewController 嵌入在导航控制器中。
Now the code looks something like this.
现在代码看起来像这样。
override func prepareForSegue(segue: UIStoryboardSegue?, sender: AnyObject!) {
if (segue?.identifier == "home_to_search") {
var searchKeyword = txtSearchBarHome.text
var svc = segue?.destinationViewController as! SearchViewController;
svc.toPassSearchKeyword = searchKeyword;
//let nav = segue?.destinationViewController as! UINavigationController
//let svc = nav.topViewController as! SearchViewController
//svc.toPassSearchKeyword = searchKeyword;
}
}
I have already explored these questions DestinationViewController Segue and UINavigationController swift, How do I segue values when my ViewController is embedded in an UINavigationController?with no luck.
我已经探讨了这些问题 DestinationViewController Segue 和 UINavigationController swift，当我的 ViewController 嵌入到 UINavigationController 中时，我如何转义值？没有运气。
What makes me wonder is that I already have ViewControllers embedded in Navigation Controllers that I can pass parameters by segueing. However, in this case it throws a Could not cast value of type 'UINavigationController'error. If I try the commented code above it does not throw an error there, but at the AppDelegateclass.
让我感到奇怪的是，我已经在导航控制器中嵌入了 ViewControllers，我可以通过 segueing 传递参数。但是，在这种情况下，它会引发“UINavigationController”类型的无法转换值错误。如果我尝试上面的注释代码，它不会在那里抛出错误，而是在AppDelegate类中抛出错误。
回答by Semih Yagcioglu
Answering my own question. In this case we need to access the child view by doing something like this:
回答我自己的问题。在这种情况下，我们需要通过执行以下操作来访问子视图：
let nav = segue?.destinationViewController as! UINavigationController
let svc = nav.topViewController as! SearchViewController
svc.toPassSearchKeyword = searchKeyword;
回答by Json
Based on Semih's answer, you can also do this to pass a variable to next segue if you don't want to use an identifier:
根据 Semih 的回答，如果您不想使用标识符，也可以这样做以将变量传递给下一个 segue：
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if let nav = segue.destination as? UINavigationController,
let vc = nav.topViewController as? TestViewController {
vc.username = "Test"
}
}
回答by Cornelis Kuijpers
Just a quick note for those looking into this issue it has been renamed to Destination
只是给那些调查这个问题的人一个简短的说明，它已被重命名为 Destination
let nav = segue.destination as! UINavigationController
let svc = nav.topViewController as! SearchViewController
svc.toPassSearchKeyword = searchKeyword;
