18.9 Mapping for Constants

Slice constant definitions map to corresponding Objective‑C constant definitions. Here are the constant definitions we saw in Section 4.9.5 on page 103 once more:

const bool      AppendByDefault = true;
const byte      LowerNibble = 0x0f;
const string    Advice = "Don't Panic!";
const short     TheAnswer = 42;
const double    PI = 3.1416;

enum Fruit { Apple, Pear, Orange };
const Fruit     FavoriteFruit = Pear;

Here are the generated definitions for these constants:

static const BOOL EXAppendByDefault = YES;
static const ICEByte EXLowerNibble = 15;
static NSString * const EXAdvice = @"Don't Panic!";
static const ICEShort EXTheAnswer = 42;
static const ICEDouble EXPI = 3.1416;

typedef enum {
    EXApple, EXPear, EXOrange
} EXFruit;
static const EXFruit EXFavoriteFruit = EXPear;

All constants are initialized in the generated header file, so they are compile-time constants and can be used in contexts where a compile-time constant expression is required, such as to dimension an array or as the case label of a switch state­ment.