Leaving aside the issue of global variables and if they are good coding practice...
Create your string outside of any Objective-C class in a .m
file in your project:
NSString *myGlobalString = @"foo";
Then put the declaration in a header file that is included by every other file that wants to access your string:
extern NSString *myGlobalString;
OK, well I can't leave it entirely aside. Have you considered putting your "global" string somewhere else, perhaps inside your application delegate as a (possibly read-only) property?
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