Re: Access type to member procedure of instance (Object Oriented programming in Ada)

[Brian Drummond <brian@shapes.demon.co.uk>]

On Mon, 19 Nov 2012 12:22:21 -0800, ake.ragnar.dahlgren wrote:

> On Monday, November 19, 2012 10:59:42 AM UTC+1, ake.ragna...@gmail.com
> wrote:

>> This problem has it's origin in the implementation of the MVC pattern
>> for a GtkAda application. Consider the following:
...
> Additional information if needed: The spec. of the Register_Handler
> procedure in the Gtkada.Builder package is declared as:
> 
> procedure Register_Handler
>   (Builder      : access Gtkada_Builder_Record'Class;
>    Handler_Name : String;
>    Handler      : Builder_Handler);

Okay, this is looking familiar...

A previous post of mine linked at the bottom of the ada.dk tutorial 
contains the comment :

-- Having only Gtkada_Builder_Record'Class and GObject_Record'Class
-- seems restrictive. I failed to find any way to register and use 
-- the following:
--    procedure Destroy(Object : access Gtk_Widget_Record'Class);
-- eventually resorting to Gtk.Builder.Get_Widget in the procedure body.
-- I must be missing something here...

To expand on that; clearly everything is a subclass of GObject_Record, 
and therefore the intent must be that anything more complex like your 
On_Quit example be registered as an Object_Handler not a Builder_Handler.

--   type Builder_Handler is access procedure
--     (Builder : access Gtkada_Builder_Record'Class);
--   type Object_Handler is access procedure
--     (User_Data : access GObject_Record'Class);

The remaining question would be ... how?

It might be worth putting your On_Quit handler into the tutorial example, 
and asking "How do I register this as an Object_Handler?" on the GtkAda 
mailing list.

- Brian