Inheritance not using STI

Rails
1

Hi there,

I have a question about inheritance in Rails.

Say you have 3 tables:

  1. pants
  2. shirts
  3. socks

Each table has different attributes, but they do share some of the same
attributes respectively in each table:

Common attributes amongst all the tables:

  1. material_used
  2. color
  3. manufacture

Different attributes:

  1. pants
    • length
    • waist_size
  2. shirts
    • sleeve_length
    • neck_size
  3. socks
    • foot_size
    • is_striped (say this is a boolean value)

Now say someone is browsing through your online clothing store buying
socks,
shirts and pants and they’re having a great time. When displaying all
items
in their cart, each line item is of a different product type
technically,
but yet they all share a few of the same attributes (material_used,
color,
manufacture).

Would it be wise to create a general Product class that stores the
common
attributes which is used for the initial @user.products query (assuming
you
have a valid User object and the superclass Product exists), and then
each
product type would inherit from Product.
class Product;end # initialize common attributes somehow
class Pants < Product;end # specify specific attributes
class Shirts < Product;end # specify specific attributes
class Socks < Product;end # specify specific attributes
etc…

I guess I’m a little confused on the best way to keep it simple (as well
as
how to create the Product class, which I think is a proxy class hooked
up to
ActiveRecord somehow… ?) when iterating through the clothes to see
what
kind of attributes they have and then display the proper info. I’d like
to
keep as much business logic out of the view as possible. Obviously Pants
don’t have an attribute called “foot_size”. I don’t have the option of
changing the database tables too much, so STI is a no-go for this
project.
I’m thinking more of going the class table inheritance route, but I’m
not
sure.
(P of EAA: Class Table Inheritance).

Are there any tutorials that cover what I’m talking about? If it
matters,
I’m stuck with Oracle. Did any of this make sense or am I on crazy
pills?

Thank you,
Dave

2

Dave,

Have a look to: http://clti.rubyforge.org/

Jean-Etienne

3

Hey,

right now Rails doesn’t seem to support CTI. There’s a plugin for
PostgreSQL, but if you are stuck to Oracle this might not work (http://
clti.rubyforge.org/).
As discussed here (http://groups.google.de/group/rubyonrails-talk/
browse_thread/thread/8d4159425d094cd9), the only way is to create a
full table for all subclasses and/or set the relations manually.
I’m now running in this problem too with a project, so I maybe write
later, how I fixed it.

Regards,

Mike

4

Thanks Jean-Etienne and Mike for the info. I’ll take a look at
clti.rubyforge.org. I know it doesn’t work with oracle, but it might be
easily extended.

-Dave