I have a preprocessor macro defined in build settings
#define FOOLITERAL @"FOO" //want FOOLITERAL to have the value of @"BAR"
Use the stringizing operator
# to make a C string out of the symbol. However, due to a quirk of the preprocessor, you need to use two extra layers of macros:
#define FOO BAR #define STRINGIZE(x) #x #define STRINGIZE2(x) STRINGIZE(x) #define FOOLITERAL @ STRINGIZE2(FOO) // FOOLITERAL now expands to @"BAR"
The reason for the extra layers is that the stringizing operator can only be used on the arguments of the macro, not on other tokens. Secondly, if an argument of a macro has the stringizing operator applied to it in the body of the macro, then that argument is not expanded as another macro. So, to ensure that
FOO gets expanded, we wrap in another macro, so that when
STRINGIZE2 gets expanded, it also expands
FOO because the stringizing operator does not appear in that macro's body.