From: Daniel <danielnorberto@gmail.com>
Subject: Re: Visibility issue
Date: Mon, 14 Sep 2020 04:33:34 -0700 (PDT) [thread overview]
Message-ID: <27269975-58eb-407b-98ca-344bee6894d2n@googlegroups.com> (raw)
In-Reply-To: <rjgor5$fhs$1@gioia.aioe.org>
Thank you for your answer Dmitry. Let me focus and change my example to easier go to the problem. I will write some question to your answer at the end of the example.
I didn't write it in the example for simplicity, but the user has to set a callback function.
This callback function is triggered in the internal implementation hierarchy packages. Let me show you the code within questions inside comments:
--- API SIDE: -----
package API.Callbacks
type Handle is tagged private
type pointer_to_Procedure is access procedure (Self : API.CAllbacks.Handle );
procedure Set_Callback (Self: in out API_HandleCallBack; cp: CallbackProcedure );
private
type Handle is tagged record
Hidden : Natural;
end record;
procedure Hidden_constructor (S: in out Handle'Class ; Hidden_content :Natural);
---------------
----- IMPLEMENTING SIDE: --------
private with API.Callbacks;
package body Internal.TASKS_Callbacks is
task body Caller is
MyHandle : API.Handle;
cp: CallbackProcedure := Get_from_pool_of_callbacks;
begin
Hidden_Constructor (MyHandle, 6);
--Cannot access to private part for API.Handle from here :(
-- compiler says that Hidden_Constructor is not a visible entity of" Callbacks"
-- I just wanted to build it to later call to the procedure:
cp (MyHandle);
end Caller;
> Why is this a primitive operation? I would consider rather
>
> function Access_to_hide_content return User_type'Class;
>
> In presence of potential overriding things like these are usually
> class-wide.
Using the updated example I've tried to use an Hidden_constructor using class-wide but compiler says
>"Hidden_Constructor" is not a visible entity of API.Callbacks.
.
> You can also use aggregation:
> type User_type is tagged with private;
> private
> type User_type is tagged with record
> Implementation : Private_Stuff;
> end record;
>
> Private_Stuff may have its own hierarchy. This pattern works well with
> limited types. You want the interface being non-limited, but the
> implementation of limited in order to control/prevent excessive copying
> and support in-place updates. So you make the interface a holder or a
> smart pointer to the reference-counted implementation.
Thank you for the idea, but I don't know if its really possible for the callback action I need to "call".
Lets say i extend Handle outside of API package hierarchy:
private with API.Callbacks;
package Internal.TASKS_Callbacks is
type Handle_child is new API.Calbacks.Handle with null record;
procedure Hidden_constructor (S: in out Handle_child; Hidden_content :Natural);
-------
package body Internal.TASKS_Callbacks is
task body Caller is
MyHandle : Handle_child;
mycall: CallbackProcedure := Get_from_pool_of_callbacks;
begin
Hidden_Constructor (MyHandle, 6);
-- But now i need to trigger the callback procedure and that procedure is defined using Handle type, not the child Handle_child
-- how can i call the original callback procedure???
-- if I do the next
mycall (MyHandle); --it raises that expect the father, not the child:
end task;
As you see.. how can i call from here the User callback procedure?
next prev parent reply other threads:[~2020-09-14 11:33 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-11 10:37 Visibility issue Daniel
2020-09-11 11:51 ` Maxim Reznik
2020-09-11 20:11 ` Daniel
2020-09-11 14:23 ` Jeffrey R. Carter
2020-09-11 20:17 ` Daniel
2020-09-11 22:36 ` Jeffrey R. Carter
2020-09-14 10:47 ` Daniel
2020-09-14 16:10 ` Jeffrey R. Carter
2020-09-15 19:11 ` Daniel
2020-09-15 20:03 ` Jeffrey R. Carter
2020-09-11 21:05 ` Dmitry A. Kazakov
2020-09-14 11:33 ` Daniel [this message]
2020-09-14 14:42 ` Dmitry A. Kazakov
2020-09-15 19:35 ` Daniel
2020-09-16 7:14 ` Dmitry A. Kazakov
2020-09-16 10:23 ` Daniel
2020-09-16 10:58 ` Dmitry A. Kazakov
2020-09-16 14:35 ` Daniel
2020-09-16 14:49 ` Jeffrey R. Carter
2020-09-16 15:05 ` Dmitry A. Kazakov
2020-09-16 20:09 ` Daniel
2020-09-16 21:48 ` Simon Wright
2020-09-17 13:31 ` Daniel
2020-09-17 15:00 ` Dmitry A. Kazakov
2020-09-17 15:32 ` Daniel
2020-09-17 16:47 ` Dmitry A. Kazakov
2020-09-18 8:05 ` Simon Wright
2020-09-14 16:18 ` Simon Wright
2020-09-17 15:58 ` Jere
2020-09-17 16:10 ` Jere
2020-09-18 8:08 ` Simon Wright
2020-09-17 21:47 ` Shark8
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