Re: Ada 95 constructors on limited types

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

On Wed, 2 Jan 2008 06:31:39 -0800 (PST), shaunpatterson@gmail.com wrote:

> I am trying to write a constructor that will return an access type to
> a new object.
> 
> What I what is something like:
> 
> procedure Test is
> 
>   Test_Pointer : Parent.Class_Access := new Parent.Child.Create (5);

Test_Pointer := Parent.Child.Create (5);

> begin
>    null;
> end Test;
> 
> Parent.ads:
> 
> package Parent is
> 
>    type Class is abstract tagged limited null record;
>    type Class_Access is access all Class'Class;

I would not use "access all" unless you need some instances of Class
allocated on the stack. But that's aside.

> end Parent;
> 
> package Parent.Child is
> 
>    type Class is new Parent.Class with private;
> 
>      function Create (Test_Value : Integer) return Class_Access;
> --   function Create (Test_Value : Integer) return Class;
> 
> private
>    type Class is new Parent.Class with
>      record
>         Value : Integer := 0;
>      end record;
> 
> end Parent.Child;
> 
> package body Parent.Child is
> 
>     function Create (Test_Value : Integer) return Class_Access is
>     begin
>          return new Class' (Value => Test_Value);
>          -- Works only with Ada 2005... I am stuck using Ada 95

   Result : Class_Access := new Class;  -- Allocation
   This : Class renames Class (Result.all); -- Downcasting
begin
   This.Value := Test_Value; -- Initialization
   return Result;

>     end Create;
> 
> end Parent.Child;

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de