Question

This question is out of pure curiosity. How does Cocoa define the id type? Is it just a typedef for a void *? Also, if you know which header file it is defined in, I would be interested in taking a look.

Answer 1

Hold down the command key and double click on any highlighted term to jump to its definition.

typedef struct objc_class *Class;
typedef struct objc_object {
    Class isa;
} *id;


typedef struct objc_selector    *SEL;    
typedef id          (*IMP)(id, SEL, ...);