UINavigation 控制器数组错误
我只是想知道弹出 UINavigationController 时遇到的一个错误。无论我当前使用哪个 UIViewController，我都实现了一个注销控制器，该控制器会弹出到 UINavigationController 中的根控制器。此处列出了执行此操作的主要代码。
NSLog(@"Root Controller: %@", [[self.navigationController.viewController objectAtIndex:0] class]);
[self.navigationController popToViewController:[self.navigationController.viewControllers objectAtIndex:0] animated:YES];
NSLog(@"Root Controller: %@", [[self.navigationController.viewController objectAtIndex:0] class]);
这是控制台显示的内容。
Root Controller: DetailViewController
Root Controller: (null)
但是，当我将上面的代码更改为：
NSLog(@"Root Controller: %@", [[self.navigationController.viewController objectAtIndex:0] class]);
[self.navigationController popToViewController:[self.navigationController.viewControllers objectAtIndex:1] animated:YES];
NSLog(@"Root Controller: %@", [[self.navigationController.viewController objectAtIndex:0] class]);
控制台中的结果显示为：
Root Controller: DetailViewController
Root Controller: DetailViewController
为什么当我将 UINavigationController 弹出到 DetailViewController 时，它没有触发 ViewWillAppear 方法来更新我的登录信息，这让我困扰了一段时间。在我看来，当我弹出到 0 索引时，它正在访问一个越界的数组对象，但是当我弹出到索引 1 时，这就是当前根控制器所在的位置。有谁知道这会是什么原因？
I was just wondering about a bug I came across when popping my UINavigationController. Whatever UIViewController I am currently in, I have implemented a logout controller that pops back to the root controller in my UINavigationController. The main code that does this is listed here.
NSLog(@"Root Controller: %@", [[self.navigationController.viewController objectAtIndex:0] class]);
[self.navigationController popToViewController:[self.navigationController.viewControllers objectAtIndex:0] animated:YES];
NSLog(@"Root Controller: %@", [[self.navigationController.viewController objectAtIndex:0] class]);
This is what the console displays.
Root Controller: DetailViewController
Root Controller: (null)
However when I change the above code to:
NSLog(@"Root Controller: %@", [[self.navigationController.viewController objectAtIndex:0] class]);
[self.navigationController popToViewController:[self.navigationController.viewControllers objectAtIndex:1] animated:YES];
NSLog(@"Root Controller: %@", [[self.navigationController.viewController objectAtIndex:0] class]);
The results in the console is displayed as:
Root Controller: DetailViewController
Root Controller: DetailViewController
It was bothering me for a while why when I popped the UINavigationController to the DetailViewController that it didnt fire the ViewWillAppear method to update my login information. It seems to me that when I pop to the 0 index it is accessing an array object that is out of bounds but when I pop to index 1, thats where the current root controller is. Does anyone know what the cause of this would be?
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我的猜测是，在将
self从堆栈中弹出后，self.navigationController被设置为 nil。如果是这种情况，看起来弹出到索引 1 处的视图控制器不会将 self.navigationController 重置为 nil （因为
self 是索引 1 处的视图控制器，或者viewWill|Did?Appear 中的一些调用正在再次设置它）。My guess is that
self.navigationControlleris being set to nil afterselfis popped off the stack.If that's the case, it looks like popping to the view controller at index 1 does not reset
self.navigationControllerto nil (either becauseselfis the view controller at index 1 or some call in viewWill|Did?Appear is setting it again).