Question

Possible Duplicate:
obj-c duplicate symbol for header variable

I have multiple .m and .mm files in my project. I can include this .h file (that dosent have a corresponding .m or .mm file) in as many .m files as I like but when I include it in more than one .mm file I get the duplicate symbols linker error.

Also in the .h file I have surrounded the content with preprocessor commands (Are these respected in obj-c?) here is what it mostly looks like:

#ifndef _CONFIG_H_
#define _CONGIF_H_

CGFloat WIDTH, HEIGHT;
// other similar code...

#endif

I get the duplicate symbols error on WIDTH and HEIGHT

Answer 1

You should add

extern

keyword before CGFloat declaration in the header, and define the variables without extern in the .m file to avoid defining your variables in multiple places.

In the header:

extern CGFloat WIDTH, HEIGHT;

In a .m file (one of them, any one)

CGFloat WIDTH, HEIGHT;