Question

Is there any way to use global int constants in Objective C that work in a case/switch statement? The technique here (http://stackoverflow.com/questions/538996/constants-in-objective-c) lets me access the constants everywhere, but does not let me put them into a switch statement.

in .h

FOUNDATION_EXPORT const int UNIT_IDLE;
FOUNDATION_EXPORT const int UNIT_DEFEND;

in .m

int const UNIT_IDLE = 0;
int const UNIT_DEFEND = 1;

Error is “Expression is not an integer constant expression”

Answer 1

I usually use enumerations with typedef statements when using constants which I will use in a switch statement.

For example, this would be in a shared .h file such as ProjectEnums.h:

enum my_custom_unit
{
    MyCustomUnitIdle    = 1,
    MyCustomUnitDefend  = 2
};
typedef enum my_custom_unit MyCustomUnit;

I can then use code similar to the following switch statement in my .c, .m, .cpp files:

#import "ProjectEnums.h"

- (void) useUnit:(MyCustomUnit)unit
{
    switch(unit)
    {
        case MyCustomUnitIdle:
        /* do something */
        break;

        case MyCustomUnitDefend:
        /* do something else */
        break;

        default:
        /* do some default thing for unknown unit */
        break;
    };
    return;
};

This also allows the compiler to verify the data being passed to the method and used within the switch statement at compile time.