Hello, last days i investigated three ORM frameworks: ActiveRecords,
DataMapper and Og.
And found that they all shares almost same limitations (when i write
'support' i mean that tool allows to solve task 'simply' and
'effectively').

1. Inheritance support.
None of these frameworks hasn't inheritance support. You forced either
by 'single table inheritance' (suitable only for similar objects) or you
can use 'multiple tables' but lose polymorphism ('Parent.find(...)'
searches only in 'parent' table and do not searches in his children's
tables).

2. 'General reference'.
So, one object can make reference to any other object. For example
'Catalog' has 'content' reference, that references 'Article', 'Image',
'File'.
ActiveRecords - support, Og - partly, DM not, as far as i know.

3. Single ID space.
The continuation to 'General reference'. Ability to find object only by
his ID.
db.find(ID)
No matter is it Article, User or something else.

I really miss these features :-(.

The question is - is there any materials or article with explanations
how to implement all these features the best way?

Thanks!
--
Posted via http://www.ruby-forum.com/.

Alexey Petrushin wrote:
> Hello, last days i investigated three ORM frameworks: ActiveRecords,
> DataMapper and Og.
> And found that they all shares almost same limitations (when i write
> 'support' i mean that tool allows to solve task 'simply' and
> 'effectively').
>
> 1. Inheritance support.
> 2. 'General reference'.
> 3. Single ID space.

Does Hibernate have all these features? Because there's an
ActiveHibernate project out there currently not moving forward. I'd love
to see some folks continue working on it, putting a nice Ruby face on
top of Hibernate.

http://code.google.com/p/activehibernate/

- Charlie

On Jun 8, 11:57am, Alexey Petrushin <axy...@gmail.com> wrote:
> Hello, last days i investigated three ORM frameworks: ActiveRecords,DataMapperand Og.
> And found that they all shares almost same limitations (when i write
> 'support' i mean that tool allows to solve task 'simply' and
> 'effectively').
>
> 1. Inheritance support.
> None of these frameworks hasn't inheritance support. You forced either
> by 'single table inheritance' (suitable only for similar objects) or you
> can use 'multiple tables' but lose polymorphism ('Parent.find(...)'
> searches only in 'parent' table and do not searches in his children's
> tables).
>
> 2. 'General reference'.
> So, one object can make reference to any other object. For example
> 'Catalog' has 'content' reference, that references 'Article', 'Image',
> 'File'.
> ActiveRecords - support, Og - partly, DM not, as far as i know.
>
> 3. Single ID space.
> The continuation to 'General reference'. Ability to find object only by
> his ID.
> db.find(ID)
> No matter is it Article, User or something else.
>
> I really miss these features :-(.
>
> The question is - is there any materials or article with explanations
> how to implement all these features the best way?
>
> Thanks!
> --
> Posted viahttp://www.ruby-forum.com/.

1. Agreed. We'd (DataMapper) like to support all 3 forms, but it'll
probably be post-1.0.

2. Yes, this is possible. It's probably not all that hard either. Just
haven't come across a personal use-case.

3. Technically, same as above, but it just looks crazy to me. I don't
see DM ever supporting this, and I'd be surprised if Hibernate did
either (though I could be wrong).

So for DM at least, number 2 would involve making the Query object
accept multiple models. Easy enough. Then it's conditions and field
and links, etc methods would need to accept a model as a parameter so
the method could return the properties (table/column information)
specific to that model. Then the DataObjectsAdapter would simply map
each model in the Query object to SQL and perform a join for a UNION
statement. It would be the Query object's responsibility to pad out
uneven fields between it's models.

And that's that. I don't see it taking more than a day to implement at
most.

But again, DM's features are driven by the people willing to scratch
an itch. If that sounds like you, feel free to drop on the IRC channel
(irc.freenode.net#datamapper). As the Rubinius guys say: If you can
breath, you can get commit access.

-Sam