Re: pointers & OOP

[Matthew Heaney <matthew_heaney@acm.org>]

tmoran@bix.com (Tom Moran) writes:

> Suppose you have
>   type Root is abstract tagged ...
>   procedure Very_General(X : in out Root);
> private
>   procedure Internal_Updating(X : in out Root'class);
> and then Root has a son and a daughter
>   type Son is new Root with ...
> and 
>   type Daughter is new Root with ...
> and suppose that Son and Daughter need to use Root's Internal_Updating
> procedure.  If they are both declared in the same package as Root, no
> problem.  Even if they are declared in child packages of Root, no
> problem.  But if they are declared in truly separate packages, then
> either they cannot see Internal_Updating, or else you move
> Internal_Updating to the public part of Root's package, thus letting
> anybody see and call Internal_Updating.
>    How would you propose structuring this if you are required to have
> 1-1 package/class?

Son and Daughter go in (public) child packages.  A child has visibility
to the private part of its parent.

package Family is

  type Root is ..

private

  procedure Internal_Update ...;

end;

package Family.Sons is

  type Son is new Root with ...;

  ...

end Family.Sons;

package Family.Daughters is

 type Daughter is new Root with ...;

end Family.Daughters;