Re: access on function returning a class wide type

[Dmitry A. Kazakov <mailbox@dmitry-kazakov.de>]

On 19 Nov 2002 21:38:32 GMT, alex <xela@netcourrier.com> wrote:

>Is there a �workaround/trick� to implement this kind of think.
>
>package A is
>   type A_T is abstract tagged null record;
>   function Fa return A_T is abstract;
>   type Fa_Ptr is access function return A_T'Class;
>end A;
>
>with A;
>package B is
>  type B_T is new A.A_T with null record ;
>  function Fa return B_T;
>end B;
>
>package body B is
>  function Fa return B_T is
>  begin return (A.A_T with null record);
>  end Fa;
>end B;
>
>with A,B;
>procedure Test is
>   Ptr : A.Fa_Ptr := B.Fa'access; -- error :  LRM:8.6(28)
>begin null;
>end Test;
>
>The compiler is expecting a function returning a A_T�Class, ok I understand�
>But, B_T is in the A_T�Class!

You could wrap B.Fa in a function returning A_T'Class:

function Fa_b return A_T'Class is
begin
   return B.Fa;
end Fa_b;

The question is why do you need something like that? Sort of lazy
object creation?

---
Regards,
Dmitry Kazakov
www.dmitry-kazakov.de