Question

I have an objective-c/xcode project with several header and implementation files. I’d like to declare a variable that I can read and change from any file associated with the project. I tried doing extern int val = 0; in a header, but that lead to a linker error.

Would appreciate any help, thanks.

Answer 1

For storing and accessing an int in and iOS app, I recommend using NSUserDefaults.

You can set the value from anywhere in the application by

NSUserDefaults *defaults = [NSUserDefaults  standardUserDefaults];
[defaults setInteger:anInt forKey:@"IntKey"];
[defaults synchronize];

Then you can retrieve the value from anywhere in the application by

NSUserDefaults *defaults = [NSUserDefaults  standardUserDefaults];
int a = [defaults integerForKey:@"IntKey"];

This also works great for BOOL, float, NSString and NSArray. Check out the NSUserDefaults documentation for more details and examples.