Rails - Oct 2006 - Drowning in underscores and foreign keys

Hi everybody,

I''m working with a legacy schema where they saw fit to underscore 
everything in sight, and I''m wondering if that''s screwing up
my
associations.

I have a table COMMUNITY_TABLE that has a COMMUNITY_ID as well as a 
COMMUNITY_TYPE_ID.  COMMUNITY_TYPE_ID is a pointer to the 
COMMUNITY_TYPE_TABLE, which has a COMMUNITY_TYPE_ID as its primary key, 
as well as a string COMMUNITY_TYPE_TABLE.  I am translating this as 
"CommmunityType has_many Communities, and Community belongs_to 
CommmunityType":

class CommunityType < ActiveRecord::Base
 set_table_name "COMMUNITY_TYPE_TABLE"
 set_primary_key "COMMUNITY_TYPE_ID"

 has_many :communities
end

class Community < ActiveRecord::Base
 set_table_name "COMMUNITY_TABLE"
 set_primary_key "COMMUNITY_ID"

 belongs_to :community_type
end


What I''d like to do is is start at a community type where my title is 
"Private" (for example), and then get all the communities that are of 
that type:

CommunityType.find_by_community_type_title("Private").communities

But this always returns [].  I know I must be missing something but I 
can''t figure out what.  I know that I have data, because I can do this:

Community.find(:first, :conditions=>["community_type_id=?", 
CommunityType.find_by_community_type_title("Private").community_type_id])

and have it return a value.  Similarly I can do this:

Community.find_first.community_type.community_type_title

And have it give back the right answer.  So Community knows that it has 
a pointer into CommunityType, but not the other way around.

Anybody know what probably obvious thing I''ve missed?

Thanks,

 D


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First off: Did you have a typo when saying:
"s a pointer to the
COMMUNITY_TYPE_TABLE, which has a COMMUNITY_TYPE_ID as its primary key,
as well as a string COMMUNITY_TYPE_TABLE."
did you mean "as a string "COMMUNITY_TYPE_TITLE" ? cos i never
saw that
title you refer to later anywhere in that explenation

Second: I''m pretty new to this stuff myself, so i just throw in my 2
cents, no promise it will work:

Tird: try this:

class CommunityType < ActiveRecord::Base
  set_table_name "COMMUNITY_TYPE_TABLE"
  set_primary_key "COMMUNITY_TYPE_ID"

  has_many :communities, :foreign_key => "community_type_id"

end

class Community < ActiveRecord::Base
  set_table_name "COMMUNITY_TABLE"
  set_primary_key "COMMUNITY_ID"

  belongs_to :community_type, :foreign_key => "community_type_id"
end

i''m not sure if you have to specify :foregn_key in the belongs_to, but
for sure in the has_many, cos otherwise Rails would assume that the
foreign_key in the COMMUNITY_TABLE would be the primary key
"community_id", but its "community_table_id"

... or i got you wrong or all twisted up :-D Give it a shot.


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> as well as a string COMMUNITY_TYPE_TABLE."
> did you mean "as a string "COMMUNITY_TYPE_TITLE" ? cos i
never saw that
> title you refer to later anywhere in that explenation
Yes, should have said COMMUNITY_TYPE_TITLE.  See what I mean about 
drowning in it? :)
>   has_many :communities, :foreign_key => "community_type_id"
>   belongs_to :community_type, :foreign_key =>
"community_type_id"
> i''m not sure if you have to specify :foregn_key in the belongs_to,
but
> for sure in the has_many, cos otherwise Rails would assume that the
> foreign_key in the COMMUNITY_TABLE would be the primary key
> "community_id", but its "community_table_id"
Didn''t fix it.  I''m not sure you''re accurate there,
though -- if I''ve
said that table B has_many A''s, then I believe the expected behavior is
to find B_id inside the A table, not A_id.  A_id would be the primary 
key for A, so B couldn''t use that to find A''s that belonged to
B.

Thanks for the ideas,
  D


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