Rails - Mar 2005 - understanding single table inheritance

Hi,

I have the following two models:

class Product < ActiveRecord::Base; end
class Book < Product; end

Product has "name", "type" fields.
Book has "isbn", "product_id" fields.

In my view for /books/list.rhtml, I am unable to use <%= book.isbn %> to 
access the "isbn" attribute of book.
I am able to use <%= book.name %> though (which the book inherited from 
product).
In my view for /products/list.rhtml, I am unable to use <%= product.isbn
%>
So am I reduced to being able to access only the parent class''
attributes?

How does one access the object attributes with single-table inheritance?

Regards,
Pb

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On Tue, 29 Mar 2005 15:43:04 +0000, Pranav Bihari
<pbihari-PkbjNfxxIARBDgjK7y7TUQ@public.gmane.org>
wrote:
> Hi,
> 
> I have the following two models:
> 
> class Product < ActiveRecord::Base; end
> class Book < Product; end
> 
> Product has "name", "type" fields.
> Book has "isbn", "product_id" fields.
> 
> In my view for /books/list.rhtml, I am unable to use <%= book.isbn %>
to
> access the "isbn" attribute of book.
> I am able to use <%= book.name %> though (which the book inherited
from
> product).
> In my view for /products/list.rhtml, I am unable to use <%= product.isbn
%>
> So am I reduced to being able to access only the parent class''
attributes?
> 
> How does one access the object attributes with single-table inheritance?
I believe that Single Table Inheritance uses the same table.  So in
your example, Book is using products, which has no isbn field.

I think you want to use associations.  Product has_many books and a
Book belongs_to a Product.

http://rails.rubyonrails.com/classes/ActiveRecord/Associations/ClassMethods.html


-- 
rick
http://techno-weenie.net