increase array in module - module

Question

I am trying to write a small module/class in Fortran. The idea is very basic:
Create and initialize the object with a dedicated constructor
Add a new element inside of it
I already write Fortran but only subroutine and I will try to use oriented object principle. Currently I have two errors:
the constructor I built does not work (seems to not accept my input arguments)...
the add_bb procedure is not accepted.
MNWE:
module test_mod
implicit none
type :: bb
real :: item
real,allocatable :: vect(:)
end type bb
interface bb
procedure :: new_bb!,add_bb
end interface bb
contains
type(bb) function new_bb(val,nbv)
real, intent(in) :: val
integer, intent(in) :: nbv
integer :: ii
new_bb%item=val
allocate(new_bb%vect(nbv))
print *,nbv
do ii=1,nbv
new_bb%vect(ii)=val
print *,ii
enddo
print *,new_bb%vect
end function new_bb
type(bb) function add_bb(it)
real,intent(in) :: it
integer :: sp
real,allocatable :: tmp(:)
sp=size(add_bb%vect)+1
allocate(tmp(sp))
tmp(1:sp-1) = add_bb%vect(1:sp-1)
call move_alloc(tmp, add_bb%vect)
add_bb%vect(sp)=it
end function add_bb
end module test_mod
program test
use test_mod
implicit none
type(bb) :: cc
cc=bb(10,20)
call cc%add_bb(10)
print *,cc%item
print *,cc%vect
!
end program test

Answer 1

I tried to fix the bugs in your code, but as I worked on it more, I discovered more and more fundamental flaws in your code. Obviously, that implies that you are likely not well familiar with OOP, in particular, in Fortran. Therefore, I recommend you to grab a book, for example, "Modern Fortran Explained" by Metcalf et al. and learn this topic. Meanwhile, here is a revised version of your code that at least works without syntax error:
module test_mod
implicit none
type :: bb_type
real :: item
real, allocatable :: vect(:)
contains
procedure, pass :: add_bb
end type bb_type
interface bb_type
procedure :: construct_bb
end interface bb_type
contains
function construct_bb(val,nbv) result (bb)
real, intent(in) :: val
integer, intent(in) :: nbv
type(bb_type) :: bb
integer :: ii
bb%item=val
allocate(bb%vect(nbv))
print *,nbv
do ii=1,nbv
bb%vect(ii)=val
print *,ii
enddo
print *,bb%vect
end function construct_bb
subroutine add_bb(self,it)
class(bb_type), intent(inout) :: self
real,intent(in) :: it
integer :: sp
real, allocatable :: tmp(:)
sp=size(self%vect)+1
allocate(tmp(sp))
!tmp(1:sp-1) = self%vect(1:sp-1)
!call move_alloc(tmp, self%vect)
!self%vect(sp)=it
end subroutine add_bb
end module test_mod
program test
use test_mod
implicit none
type(bb_type) :: cc, dd
cc=bb_type(10,[20])
call dd%add_bb(10.0)
print *,cc%item
print *,cc%vect
!
end program test