Question

I have this code that defines struct (incoming is simple struct)

#define FUNCS_ARRAY 3

    struct func
    {
        void (AA::*f) (incoming *);
        int arg_length;
    };

    func funcs[FUNCS_ARRAY];

then in class AA body i define the pointer Array like this :

funcs[0] = { &AA::func1, 4 };
funcs[1] = { &AA::func2, 10 };
funcs[2] = { &AA::func2, 4 };

when i try to call one of the functions via the array im getting compilation error:
if i call it like this (p is incoming ):

(*funcs[p->req]->*f)(p);  

im getting this error:

error: no match for ‘operator*’ in ‘*((AA*)this)->AA::funcs[((int)p->AA::incoming::req)]’

when i try to call it like this :
(funcs[p->req]->*f)(p);
im getting :

error: ‘f’ was not declared in this scope

when i try this :

   (funcs[p->req].f)(p);

error: must use ‘.*’ or ‘->*’ to call pointer-to-member function in ‘((AA*)this)->AA::funcs[((int)p->AA::incoming::req)].AA::func::f (...)’, e.g. ‘(... ->* ((AA*)this)->AA::funcs[((int)p->AA::incoming::req)].AA::func::f) (...)’

what is the right way to access the function pointer in side the struct ?

Answer 1

To call a member function through a pointer-to-member-function you need that pointer and an instance of the appropriate class.

In your case, the pointer-to-member is funcs[i].f, and I’ll assume you have an instance of AA called aa. Then you can call that function like this:

(aa.*(funcs[p->req].f))(p);

If aa is a pointer-to-AA, then the syntax would be:

(aa->*(funcs[p->req].f))(p);

If you’re calling from within a (non-static) member function of AA, then try:

(this->*(funcs[p->req].f))(p);