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)