how to declare a variable as extern in objectivec,so that i can access that in any view controller

Question

i want to access the same variable in all view controllers ....

Answer 1

extern is a C keyword, and works the same in Objective-C as in straight C. In your header file, declare your variable:

extern NSString *myGlobal;

And then set it in your .m file.

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.

Answer 2

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.

Answer 3

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.