如何从选项卡栏控制器访问视图控制器？
我有一个选项卡栏控制器，每个选项卡都包含一个导航控制器。
如何访问选项卡中导航控制器中的特定视图控制器，以便访问特定于该视图控制器的属性？
我尝试了以下代码：
//Get the navigation controller of the 3rd tab
self.tabController.selectedViewController
= [self.tabController.viewControllers objectAtIndex:2];
//Attempt to retrieve the viewcontroller I want from the tabcontroller
SomeViewController *svc = (SomeViewController *)self.tabController.selectedViewController;
//Attempting to access a BOOLEAN property in svc viewcontroller
svc.someProperty = YES;
上面的代码失败了，因为似乎“self.tabController.selectedViewController”返回了我一个导航控制器。如何扩展代码以便可以访问“svc.someProperty”？
I have a tab bar controller and each tab consist of a navigation controller.
How can I access a specific view controller in a navigation controller in a tab so that I can access a property specific to the view controller?
I tried the following code:
//Get the navigation controller of the 3rd tab
self.tabController.selectedViewController
= [self.tabController.viewControllers objectAtIndex:2];
//Attempt to retrieve the viewcontroller I want from the tabcontroller
SomeViewController *svc = (SomeViewController *)self.tabController.selectedViewController;
//Attempting to access a BOOLEAN property in svc viewcontroller
svc.someProperty = YES;
The above code failed because it seems that "self.tabController.selectedViewController" returns me a navigation controller. How can I extend the code so that I can access "svc.someProperty"?
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您可以使用 < code>-topViewController 从导航控制器获取视图控制器（或 <代码>-visibleViewController< /code> 如果您使用的是模态视图控制器）。
You can use
-topViewControllerto get the view controller from the navigation controller (or-visibleViewControllerif you are using modal view controllers).如果 self.tabController.selectedViewController 是您的导航视图控制器，那么您可以使用以下方法访问当前可见的控制器：
visibleViewController和顶视图控制器使用：
topViewController如果这不是允许您访问
SomeViewController，您可以迭代导航控制器堆栈上推送的控制器列表：viewControllersIf
self.tabController.selectedViewControlleris your navigation view controller, then you can access the currently visible controller using:visibleViewControllerand the top view controller using:
topViewControllerIf this does not allow you to get to
SomeViewController, you can iterate through the list of controllers pushed on the navigation controller stack:viewControllers由于视图控制器是返回的 UINavigationController(SVC) 的子视图，因此您只需向其发送以下方法
[svc topViewController];。这应该返回视图控制器，然后您应该能够访问该属性。Since the view controller is a subview of the returned UINavigationController(SVC), you could just send it the following method
[svc topViewController];. That should return you the view controller and then you should be able to access the property.