Re: Destructor question

[Matthew Heaney <matthew_heaney@acm.org>]

Rusnak <bogus@nowhere.com> writes:

> How are destrcutor methords properly implemented in Ada on tagged
> records?  I have the following setup:
> 
>     Given a tagged record type:
> 
>        type Instance is abstract tagged
>            record
>               ...
>           end record;
> 
>       type Object is access all Instance;
> 
>       type Class_Object is access all Instance'Class;
> 
>   and a package which keeps a container of "Class_Object"s.
> 
>    At the end of the day, I need to deallocate all the objects in the
> container.

Hers's an idea:

generic
   type Item_Type is tagged private;
package Containers is

   type Container_Type is limited private;

   procedure Add 
     (Item : in     Item_Type'Class;
      To   : in out Container_Type);
      
...
private
 
  type Item_List is <list of pointers to Item_Type'Class>;

  type Container_Type is
     new Ada.Finalization.Controlled with record
       Items : Item_List;
     end record;

  procedure Finalize (Container : in out Container_Type);

end Containers;

package body Containers is

  procedure Finalize (Container : in out Container_Type) is
  begin
    <remove all items in Container.Items>
  end;

...
end Containers;