Re: Private extension of a synchronized interface

[Simon Wright <simon@pushface.org>]

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Jere <jhb.chat@gmail.com> writes:

> In the other part that I commented out I was trying to add a publically
> available override to the interface operation, but haven't been successful.
> Do you know of any syntax changes I might need to do to:
>
>         -- The following lines give the errors:
>         -- "p1" conflicts with declaration at line xxx
>         -- and
>         -- missing body for "p1"
>        
>         --overriding
>         --procedure p1(Self : in out Instance); 
>
> So I don't need to always dispatch?

I'm not 100% sure why this works & the other doesn't - I think because
Instantiation.P1 is actually publicly visible.

Also not sure whether you could do away with the inner Instantiation.

Anyway,


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with Ada.Text_IO; use Ada.Text_IO;

procedure Hello is

   package Example is

      type An_Interface is synchronized interface;
      procedure P1 (Self : in out An_Interface) is abstract;

      package Instantiation is

         type Instance is synchronized new An_Interface with private;

         overriding
         procedure P1 (Self : in out Instance);

      private

         protected type Instance is new An_Interface with
            procedure Actual_P1;
         private
         end Instance;

      end Instantiation;

   end Example;

   package body Example is

      package body Instantiation is

         protected body Instance is
            procedure Actual_P1 is
            begin
               Put_Line("Did Something");
            end Actual_P1;
         end Instance;

         procedure P1 (Self : in out Instance) is
         begin
            Self.Actual_P1;
         end P1;

      end Instantiation;

   end Example;

   V : Example.Instantiation.Instance;

begin
   Put_Line("Hello, world!");

   --  dispatching ...
   Example.An_Interface'Class (V).P1;

   --  not dispatching
   V.P1;
end Hello;