iOS：如何获取指向导航控制器的指针
我显然错过了一些东西......
在我的 iOS 应用程序中，我将 UIViewController 推到导航控制器上：
MyViewController *mvc = [[MyViewController alloc] initWithNibName:@"MyViewController"];
[self.navigationController mvc animated:YES];
MyViewController 显示正常，我可以看到并使用导航栏，但是当我尝试从在我的视图控制器中，我得到零结果。
UINavigationController *nav = [self navigationController];
if (!nav) {
NSLog(@"no nav");
}
我一整天都在为此绞尽脑汁，但看不出我做错了什么。我在 Xcode 中没有收到任何警告或错误。我完全错过了什么吗？
蒂亚：约翰
I'm obviously missing something...
In my iOS app, I push a UIViewController onto a navigation controller:
MyViewController *mvc = [[MyViewController alloc] initWithNibName:@"MyViewController"];
[self.navigationController mvc animated:YES];
MyViewController displays fine, and I can see and use the navigationBar, but when I try to get a pointer back to the navigation controller from within my view controller, I get a nil result.
UINavigationController *nav = [self navigationController];
if (!nav) {
NSLog(@"no nav");
}
I've been beating my head against this all day, but can't see that I'm doing anything wrong. I get no warnings or errors in Xcode. Am I completely missing something?
TIA: john
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navigationController将无法在viewDidLoad上正确设置。您必须在viewDidAppear或稍后的某个阶段检查它。您在哪个方法中调用[self navigationController]？原因是当调用 viewDidLoad 时，UINavigationController 仍在处理pushViewController:animated: 方法。它似乎在初始化控制器的
view之后设置了navigationController属性。我不记得该属性是否在viewWillAppear运行时设置，但它肯定应该由viewDidAppear设置。The
navigationControllerwon't be set properly onviewDidLoad. You have to check it inviewDidAppearor at some later stage. Which method are you calling to[self navigationController]in?The reason for this is that when
viewDidLoadis called, theUINavigationControlleris still processing thepushViewController:animated:method. It would appear to set thenavigationControllerproperty after it initialises the controller'sview. I can't recall whether the property is set by the timeviewWillAppearruns, but it should definitely be set byviewDidAppear.