Declaring extern NSString causes linker error

Question

This is ridiculous, im trying to create a sound bool to turn of in app sounds. I keep getting

Undefined symbols for architecture i386:
\"_kPlaySoundPrefsKey\",         


        

Answer 1

When you declaring something as extern you are telling the compiler the type AND that you will define it somewhere else. In your case you never define your variable.

So in your .h you would have:

extern NSString* kPlaySoundPrefsKey;

But in some .m you must also have

NSString* kPlaySoundPrefsKey = @"play_sounds"; // or some value

Since in your case these are constants you can also specify:

extern NSString* const kPlaySoundPrefsKey;

and

NSString* const kPlaySoundPrefsKey = @"play_sounds"; 

The addition of the const qualifier will cause a compiler error if someone ever writes something like

kPlaySoundPrefsKey = @"some_other_value";