[Dbix-class] table-per-subclass - how it works?

[Alex Erzin]

Yes, in some cases you are right, but you are saying about "long inheritance chains" and other cases where inheritance is not enought flexible, 
but i say about just one case in one place where inheritance is preferred for me, and i try to find solution _how_ to implement inheritance, but not about _why_not_ :)


15.06.2012, 10:43, "Ben Tilly" <btilly at gmail.com>:
> The benefits of OOP are mostly in information hiding.
>
> If you're creating a bunch of long inheritance chains, you're probably
> doing OOP poorly.  Composition is preferred.  And maps *much* more
> naturally onto a relational database.
>
> On Thu, Jun 14, 2012 at 11:37 PM, Alex Erzin <eaa-home at yandex.ru> wrote:
>
>>  Hm... it really works, but where are benefits of OOP? ;)
>>  There is no inheritance at all, and to access parent's properties I should call parent directly, so inheritance just replaced with incapsulation, and it's no one what i try to find.
>>
>>  Some years ago we have implemented inheritance in ORM in some commercial project in Perl, later I have swithed to java and have found Hibernate it really cool with ORM.
>>  But now I have returned to Perl and I think that DBIx::Class can help me with ORM, but right now i'm confused that cannot find "standard" solution for typical task.
>>
>>  15.06.2012, 10:25, "Hailin Hu" <i at h2l.name>:
>>>  Is it acceptable like something below
>>>
>>>  package Target;
>>>  ...
>>>  package Host;
>>>  ...
>>>  __PACKAGE__->belong_to('target' => 'Target', 'target_id');
>>>  sub column_only_exists_in_target {
>>>    my $self = shift;
>>>    return $self->target->column_only_exists_in_target;
>>>  }
>>>
>>>  well, it is not a good solution, but it could work, I think :)
>>>
>>>  On Fri, Jun 15, 2012 at 3:04 PM, Alex Erzin <eaa-home at yandex.ru> wrote:
>>>>   Hello,
>>>>
>>>>   I need to implement table-per-class inheritance, as it simple made in Hibernate in Java (more details can be found here http://docs.jboss.org/hibernate/orm/4.1/manual/en-US/html/ch10.html#inheritance-tablepersubclass),
>>>>   but cannot find right way how to do it in DBIx::Class.
>>>>
>>>>   For example, I have two objects: Target (with properties ID, Description) and Host (ID, Hostname, IP), Host inherited from Target, and on table-level there are two tables Host and Target, joined by ID field.
>>>>
>>>>   CREATE  TABLE  `mydb`.`target` (
>>>>    `target_id` INT NOT NULL ,
>>>>    `description` VARCHAR(45) NULL ,
>>>>    PRIMARY KEY (`target_id`) )
>>>>
>>>>   CREATE  TABLE `mydb`.`host` (
>>>>    `target_id` INT NOT NULL ,
>>>>    `hostname` VARCHAR(45) NULL ,
>>>>    `ip` VARCHAR(45) NULL ,
>>>>    PRIMARY KEY (`target_id`) ,
>>>>    CONSTRAINT `fk_host_target`
>>>>      FOREIGN KEY (`target_id` )
>>>>      REFERENCES `mydb`.`target` (`target_id` )
>>>>   )
>>>>
>>>>   How to implemeng there classes Target and Host, so it possible to write
>>>>
>>>>   print $target->id(), $targer->description()
>>>>   print $host->id(), $host->description(), $host->hostname(), $host->ip()
>>>>
>>>>   ?
>>>>
>>>>   I have no ideas how to implement inheritance, and all my experiments are failed - from Host i cannot get access to parent properties like description.
>>>>   Could you help me please (with examples)?
>>>>
>>>>   Thanks.
>>>>
>>>>   --
>>>>   eaa@
>>>>
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>>
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>
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