Mimic classes in ANSI C

Question

Hi

To make a struct's members "private" to the outside I know that I can do this.

In the .h file

typedef struct Obj Obj;

In the .c file you then

struct Obj {
int a;
int b;
}

This will keep the knowledge of the existense of a and b from beeing known. But all the "member" functions in the .c file will now about them and can opperate on then. But what I wonder about now is that if you can make PART of the struct "private". Say that I want to keep those a and b variables "private" but then I want to have some function pointers that I want to remain public. Is this possible? I know that if I try to declare these in the struct in the .h file I would get a duplicate declaration error on the struct.

Answer 1

Copy Python: use the honour system for ‘private’ members.

Put a _ at the start of the member name as a red flag that other code shouldn't be touching it. Unless you've got security boundaries inside your application (which is uncommon), you don't actually need real privates, you only need a convention agreed-upon by members of your team to pretend they're private.

Try not to add complexity by forcing C into a paradigm which it doesn't really fit. Extra headers for public/private interfaces and extra source files for class management are going to make your development work more complicated, defeating the ‘more maintainable’ goal that information-hiding is aiming for.