I am not sure if I wrote the question title right, but I did a MWE to explain me better what I would like to do:
module prueba
type :: basic
class(basic),pointer :: myself => null()
contains
procedure :: hello => basic_hello
end type
type,extends(basic) :: complicated
contains
procedure :: hello => complicated_hello
end type
contains
subroutine basic_hello(a)
class(basic), target :: a
a%myself=>a ! <----- XXX
print *, 'I am basic'
end subroutine
subroutine complicated_hello(a)
class(complicated), target :: a
call a%basic%hello()
print *, 'I am complicated'
end subroutine
end module
program main
use prueba
type(complicated) :: a
call a%hello()
! Returns:
! I am basic
! I am complicated
call a%myself%hello()
! Returns:
! I am basic
end program
I would like to set the pointer a%myself in the basic level, making it polymoprhic, so then I can run any of the extended hello procedure. That is, I would like to also get "I am complicated" legend in the second call (through the pointer). This might no have sense in the MWE, but I think it actually does in my real code. Since this approach is not working, I would like to know why, and what other alternative is possible. Thank you.
The main reason is in the
call a%basic%hello()
that way you are passing a reference which is really type(basic) and hence the stored pointer in myself is just a pointer to that part that is of type(basic).
You need to do the assignment
a%myself=>a
in some context, where the a is really of dynamic type complicated even if polymorphic class(basic).
That could be in the outer scope, where you have access to the original type(complicated) variable or you could, e.g., do
call basic_hello(a)
instead of the call a%basic%hello().
This passes the a that is the argument of complicated_hello(a) instead of the a%basic.