objective c - integer constant does 'not reduce to an integer'

Question

I use this code to set my constants

// Constants.h
extern NSInteger const KNameIndex;

// Constants.m
NSInteger const KNameIndex = 0;

And in a switch statement within a file that imports the Constant.h file I have this:

switch (self.sectionFromParentTable) {
    case KNameIndex:
        self.types = self.facilityTypes;
        break;
    ...

I get error at compile that read this: "error:case label does not reduce to an integer constant"

Any ideas what might be messed up?

Answer 1

For C/C++ and Objective-C must the case statement have fixed values - "reduced to an integer (read value)" at compile time

Your constants is not a real "constant" because it is a variable and I imagine it can be changed through a pointer - ie &KNameIndex

Usually one defines constants as enum

enum {
    KNameIndex = 0,
    kAnotherConstant = 42
};

If you would use C++, or Objective-C++ (with .mm as file extension) you could use a const statement as

const int KNameIndex = 0;