duplicate symbols for architecture i386 clang

Question

I\'ve seen several posts on google and stackoverflow related to this error, I\'ve read all of them but still fetching the problem , I will be glad for a solution. Here is th

Answer 1

Taken from https://stackoverflow.com/a/2755581/190599

What you can do is put in your header (MyConstants.h):

extern const int MyConstant;
extern NSString * const MyStringConstant;

And in a source file, include the header above but define the constants (MyConstants.m):

const int MyConstant = 123;
NSString * const MyStringConstant = @"SomeString";

Then, you simply need to include the header in any other source file that uses either of these constants. The header is simply declaring that these constants exist somewhere, so the compiler won't complain, because it's the linker's job to resolve these constant names. The source file that contains your constant definitions gets compiled, and the linker sees that this is where the constants are, and resolves all of the references found in the other source files.

The problem with declaring and defining a constant in a header (that is not declared as static) is that the compiler treats it as an independent global for each file that includes that header. When the linker tries to link all of your compiled sources together it encounters the global name as many times as you have included MyConstants.h.