How to use global variables in Objective-C?

Question

How should I declare a global variable in my Objective-C project?

Answer 1

Don't. Global variables are often a sign of poor design. A common replacement in Objective-C is a class method that returns an object (that may or may not be a singleton), such as [NSUserDefaults standardUserDefaults] or [UIDevice currentDevice].

However, if you must use a global variable, read on.

In your header:

extern NSString *someString;
extern NSInteger someInteger;

In your implementation file:

NSString *someString = @"DEFAULT_VALUE";
NSInteger someInteger = DEFAULT_VALUE;