xcode 如何从 App Delegate 和/或其他视图控制器访问多个视图控制器？
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How to access multiple View Controllers from App Delegate and/or other View Controllers?
提问by Richard Williams
I suspect this is a very simple answer or I'm on totally the wrong track. I need to be able to set variables and access fields etc in a view controller from either App Delegate or another view controller.
我怀疑这是一个非常简单的答案，或者我完全走错了路。我需要能够从 App Delegate 或另一个视图控制器在视图控制器中设置变量和访问字段等。
Previously I could do this from App Delegate to my first view controller by doing the following in 'didFinishLaunchingWithOptions':
以前，我可以通过在“didFinishLaunchingWithOptions”中执行以下操作，从 App Delegate 到我的第一个视图控制器执行此操作：
viewController = (ViewController *)self.window.rootViewController;
viewController = (ViewController *)self.window.rootViewController;
After that I could/can access methods within the view controller from App Delegate by doing the normal [viewController someMethod];.
之后，我可以/可以通过执行正常的 [viewController someMethod]; 从 App Delegate 访问视图控制器中的方法。
If I have multiple view controllers (currently have 3), how can I access the other ones from other locations? Incidentally I have found SOME explanations but all talk about nib/xibs combined with code. I don't have them, I have a storyboard and code (I'm new to app dev).
如果我有多个视图控制器（目前有 3 个），我如何从其他位置访问其他视图控制器？顺便说一句，我找到了一些解释，但都在谈论 nib/xib 与代码的结合。我没有它们，我有一个故事板和代码（我是应用程序开发的新手）。
Thanks!
谢谢！
回答by Rok Jarc
In your appDelegate you can simply declare properties that will hold references to this viewControllers.
在您的 appDelegate 中，您可以简单地声明将保存对此 viewController 的引用的属性。
For example:
例如：
in AppDelegate.h
在 AppDelegate.h 中
@property (nonatomic, strong) UIViewController *vc1;
@property (nonatomic, strong) UIViewController *vc2;
in AppDelegate.m
在 AppDelegate.m 中
@synthesize vc1,vc2;
Wherever you are creating this viewControllersyou can access your appDelegateand set it's properties to hold the right reference. Don't forget to include AppDelegate.hto this file.
无论您在哪里创建它，viewControllers您都可以访问您的appDelegate并设置它的属性以保存正确的引用。不要忘记包含AppDelegate.h到这个文件中。
UIViewController *someVC = [init view controller....];
AppDelegate *appDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
appDelegate.vc1 = someVC;
And from then on you can access this viewController as appDelegate's property.
从那时起，您可以将这个 viewController 作为 appDelegate 的属性访问。
EDIT: for storyBoarding it looks like this would be safe to do in - (void)viewDidLoad.
编辑：对于 storyBoarding，在- (void)viewDidLoad.
Or an even better approach would be (as Richard mentioned) to do this in - (id)initWithCoder:(NSCoder *)decoder
或者更好的方法是（正如理查德提到的）在 - (id)initWithCoder:(NSCoder *)decoder
"When instantiating a view controller from a storyboard, iOS initializes the new view controller by calling its initWithCoder: method instead." from documentation
“当从故事板实例化一个视图控制器时，iOS 通过调用它的 initWithCoder: 方法来初始化新的视图控制器。” 来自文档
But please note, if you're changing any data from one view controller to another you might want to consider holding this data in a separate part of code (so called modelin model-view-controllerapproach). This would be the safest way to 'exchange' data between viewControllers.
但请注意，如果您要将任何数据从一个视图控制器更改为另一个视图控制器，您可能需要考虑将这些数据保存在代码的单独部分（model在model-view-controller方法中称为）。这将是在 viewController 之间“交换”数据的最安全的方式。
