[PD-dev] shared class data and functions

I have three classes: foo, bar, bow

Foo has a function:

void foo_blah(t_foo *x, t_symbol *s, t_int argc, t_atom *argv) {     if(x->x_member == 1) do_something... }

Bar and bow both have x->x_member, too, and I want all three to use the same function so I don't have to copy it two more times. Is there a way to do this:

void foo_blah(t_pd *x, t_symbol *s, t_int argc, t_atom *argv) {     if we can cast x to t_foo, t_bar or t_bow then     check if x has x->member equal to 1, and if so then do_something...

}

which I can call by sending t_foo, t_bar or t_bow as the first arg to that function?

It seems like I should be able to do this but I can't figure out all the pointer bs.

-Jonathan