Can I define a function inside a C structure? [duplicate]

Answer 1

The idea is to put a pointer to a function inside the struct. The function is then declared outside of the struct. This is different from a class in C++ where a function is declared inside the class.

For example: stealing code from here: https://web.archive.org/web/20121024233849/http://forums.devshed.com/c-programming-42/declaring-function-in-structure-in-c-545529.html

struct t {
    int a;
    void (*fun) (int * a);
} ;

void get_a (int * a) {
    printf (" input : ");
    scanf ("%d", a);
}

int main () {
    struct t test;
    test.a = 0;

    printf ("a (before): %d\n", test.a);
    test.fun = get_a;
    test.fun(&test.a);
    printf ("a (after ): %d\n", test.a);

    return 0;
}

where test.fun = get_a; assigns the function to the pointer in the struct, and test.fun(&test.a); calls it.