Where do you declare a constant in Objective-C?

Question

I declared a constant in a header file const double EARTH_RADIUS=6353; that is imported to various other headers and I got a linker error.

L         


        

Answer 1

There are two ways to accomplish this:

1st option- As previous replies pointed, in the .h file:

myfile.h
extern const int MY_CONSTANT_VARIABLE;

and in myfile.m define them

myfile.m    
const int MY_CONSTANT_VARIABLE = 5;

2nd option- My favourite:

myfile.h
static const int MY_CONSTANT_VARIABLE = 5 ;