Rails - Sep 2008 - legacy database and set_table_name

I''m trying like crazy to wrap a rails app around a legacy oracle
database.  This app will not be mutating any data in the database,
only viewing it.  Here''s a 30 second description of the
"schema".

There is a master table for a health care claim (I will call it
claim_master), and this table has a unique id for the claim, as well
as a type and a status.  Type can be 1 of about a dozen possible
values.  Status is either paid, suspended or denied.  Then we have
several other tables, split up by claim type and status, that hold
extra claims data.  So claims of type A with a paid status would be
in, say, claims_a_paid and a claim with type B  with a deny status
would be in claim_b_deny.

I want to set up my models with associations, but the association must
depend on values in the database.  Take this:

class Claim < ActiveRecord::Base
  has_one :extra
  set_table_name "claim_master"
end

class ClaimExtra < ActiveRecord::Base
  belongs_to :claim
  set_table_name "???"
end

The table name that belongs where the ??? is depends on data in the
claim.  Is there any rails magic I can use that can let this table
name be dynamically constructed out of the results from the belongs_to
directive being executed?
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I''m probably out of my depth here, but since you''re not doing
any writing, I wonder if you could get a view together on the oracle side that
UNIONS the data from your various ClaimExtra tables, and then point rails at
that as the source ''table'' for ClaimExtra?

You could maybe even get fancy and pretend to be doing Single Table Inheritance
on that view, if you wanted to e.g., have distinct DeniedTypeAClaim and
SuspendedTypeBClaim classes...

-----Original Message-----
From: rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
[mailto:rubyonrails-talk@googlegroups.com] On Behalf Of Reacher
Sent: Wednesday, September 10, 2008 12:49 PM
To: Ruby on Rails: Talk
Subject: [Rails] legacy database and set_table_name


I''m trying like crazy to wrap a rails app around a legacy oracle
database.  This app will not be mutating any data in the database, only viewing
it.  Here''s a 30 second description of the "schema".

There is a master table for a health care claim (I will call it claim_master),
and this table has a unique id for the claim, as well as a type and a status. 
Type can be 1 of about a dozen possible values.  Status is either paid,
suspended or denied.  Then we have several other tables, split up by claim type
and status, that hold extra claims data.  So claims of type A with a paid status
would be in, say, claims_a_paid and a claim with type B  with a deny status
would be in claim_b_deny.

I want to set up my models with associations, but the association must depend on
values in the database.  Take this:

class Claim < ActiveRecord::Base
  has_one :extra
  set_table_name "claim_master"
end

class ClaimExtra < ActiveRecord::Base
  belongs_to :claim
  set_table_name "???"
end

The table name that belongs where the ??? is depends on data in the claim.  Is
there any rails magic I can use that can let this table name be dynamically
constructed out of the results from the belongs_to directive being executed?


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