Re: naming, was Re: Design problem: generic package vs tagged subtype

["Marcelo Coraça de Freitas" <marcelo.batera@gmail.com>]

First I'd like to say I am sorry if my text writing isn't quite clear.
I am not a native english speaker and I haven't spoken in this
language for quite a while now.


I have come through some of those problems when I was design KOW_Ent
(another Ada ORM, which is MGPL and is based on APQ-Provider which is
a database connection pool implemented using APQ).


I decided to use tagged types all over the place (the only generic
package was for building queries and returning vectors of objects,
which is being replaced by a non-generic implenentation... well, I am
getting off topic now.. hehe).


Each persistent type extends KOW_Ent.Entity_Type (which already has an
ID, a field for storing filtering tags (in the web sence) and the
original entity tag (it is possible to extend a type further).

The columns are represented by the KOW_Ent.Entity_Property_Type. Each
data type is represented by it's very own Entity_Property_Type
implementation which holds access to a function to get the data from
the object and a procedure that sets it.

For the engine to work it is needed to register the entity type and
it's properties:


An example of code generated by a tool created to easy the development
of kow_ent based applications is:

                KOW_Ent.Entity_Registry.Register(
                                Entity_Tag      =>
teca.Entities.Content_Entity'Tag,
                                Table_Name      => "teca_contents",
                                Id_Generator    => null,
                                Factory         =>
The_Content_Entity_Factory'Access
                        );


                KOW_Ent.Entity_Registry.Add_Property(
                        Entity_Tag      =>
teca.entities.Content_Entity'Tag,
                        Property        =>
KOW_Ent.Properties.New_UString_Property(
 
Column_Name     => "title",
 
Getter          =>
teca.Entities.Content_Entity_title_hlp.getter'Access,
 
Setter          =>
teca.Entities.Content_Entity_title_hlp.setter'Access
                                                                ,Length
=> 255
                                                )
                      );

By the way, the factory is used by the web interface for handling
database data which is part of the KOW_View-Entities module.

The data loading process is done by the KOW_Ent.Load procedure:
        procedure Load( Entity : in out Entity_Type'Class; ID : in
ID_Type );

It then queries the registry and load the data - that will come from
different tables when you extend another existing entity type. The
store procedure works basically the same.


I hope my 50 cents can help you in your task.


Regards,
--
Marcelo C. de Freitas
http://framework.kow.com.br