Hiding members in a C struct

Question

I\'ve been reading about OOP in C but I never liked how you can\'t have private data members like you can in C++. But then it came to my mind that you could create 2 structu

Answer 1

You almost have it, but haven't gone far enough.

In the header:

struct SomeStruct;
typedef struct SomeStruct *SomeThing;


SomeThing create_some_thing();
destroy_some_thing(SomeThing thing);
int get_public_member_some_thing(SomeThing thing);
void set_public_member_some_thing(SomeThing thing, int value);

In the .c:

struct SomeStruct {
  int public_member;
  int private_member;
};

SomeThing create_some_thing()
{
    SomeThing thing = malloc(sizeof(*thing));
    thing->public_member = 0;
    thing->private_member = 0;
    return thing;
}

... etc ...

The point is, here now consumers have no knowledge of the internals of SomeStruct, and you can change it with impunity, adding and removing members at will, even without consumers needing to recompile. They also can't "accidentally" munge members directly, or allocate SomeStruct on the stack. This of course can also be viewed as a disadvantage.