xcode 如何在objectivec中将变量声明为extern，以便我可以在任何视图控制器中访问它
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/3409350/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
how to declare a variable as extern in objectivec,so that i can access that in any view controller
提问by Linux world
i want to access the same variable in all view controllers ....
我想在所有视图控制器中访问相同的变量....
回答by Seamus Campbell
extern is a C keyword, and works the same in Objective-C as in straight C. In your header file, declare your variable:
extern 是一个 C 关键字，在 Objective-C 中与在直接 C 中的工作方式相同。在您的头文件中，声明您的变量：
extern NSString *myGlobal;
And then set it in your .m file.
然后将其设置在您的 .m 文件中。
However, this is frequently a poor coding practice; it is generally preferable to explicitly hand your view controllers some kind of state object or data source.
然而，这通常是一种糟糕的编码实践；通常最好显式地将某种状态对象或数据源传递给您的视图控制器。
回答by Kendall Helmstetter Gelner
Instead of putting in an extern for variables, store your data in the AppDelegate instance - or in some other singleton. Then you can get to it, and modify it, from anywhere.
不要为变量放入外部变量，而是将数据存储在 AppDelegate 实例中 - 或其他一些单例中。然后，您可以从任何地方访问并修改它。
回答by ACBurk
While I'll admit I still use the AppDelegate solution quite often, I believe the singleton design pattern is a better solution. Here's a link to a solution and the reasoning.
虽然我承认我仍然经常使用 AppDelegate 解决方案，但我相信单例设计模式是更好的解决方案。这是解决方案和推理的链接。
