mattmassicotte/build_time_values.md

## build_time_values.md

      
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              build_time_values.md
            
          
    Set value

GCC_PREPROCESSOR_DEFINITIONS = FOO=My Value
Add Constants.m

It is particularly important to check that the definition of your value exists here, as it will not cause a compilation failure, but instead result in the generation of @"FOO".
@import Foundation;

#include <os/base.h>

#ifdef FOO
NSString* const MyConstant = @OS_STRINGIFY(FOO);
#else
#error Undefined
#endif
Bridging Header

@import Foundation;

extern NSString* const MyConstant;
Access it from Swift

print("value: ", MyConstant)