Rails - Aug 2006 - has_many :through a belongs_to relationship

I have users who belong to a group.  I also have a room that belongs to 
a group.  I want to use a has_many through association to link the room 
and the users as such:

class Room < ActiveRecord::Base

belongs_to :group
has_many :users, :through => :group

end

The SQL generated for the search is incorrect:

SELECT users.* FROM users  INNER JOIN group ON users.group_id = 
groups.id    WHERE (groups.group_id = 2)

The WHERE clause looks for group_id within the groups table when it 
should be looking for just id.  It uses groups.id in the inner join, so 
I don''t understand why it is wrong in the WHERE clause.  Do I need to 
specify something?

Thanks in advance for any help :-).

Chris

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Chris Rericha wrote:
> I have users who belong to a group.  I also have a room that belongs to 
> a group.  I want to use a has_many through association to link the room 
> and the users as such:
> 
> class Room < ActiveRecord::Base
> 
> belongs_to :group
> has_many :users, :through => :group
> 
> end
> 
> The SQL generated for the search is incorrect:
> 
> SELECT users.* FROM users  INNER JOIN group ON users.group_id = 
> groups.id    WHERE (groups.group_id = 2)
> 
> The WHERE clause looks for group_id within the groups table when it 
> should be looking for just id.  It uses groups.id in the inner join, so 
> I don''t understand why it is wrong in the WHERE clause.  Do I need
to
> specify something?
It could be that you''re trying to use has_many :through in an 
"unsupported configuration". You can do it where both belongs_to 
associations are in the join model, or where just one of them is, but 
you can''t do it where neither is in the join model. What do your tables
look like, and your other models?

--
Josh Susser
http://blog.hasmanythrough.com

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

What I really want to do is have the room know about all of the meetings 
for all of the users in the group.  Here are the tables.

table Group
{
   id       : int
   ...
}

table User
{
   id       : int
   group_id : int
   ...
}

table Meeting
{
   id       : int
   user_id  : int
   ...
}

table Room
{
   id       : int
   group_id : int
   ...
}

Here are the active record associations:

class Group < ActiveRecord::Base
  has_one :room
  has_many :users
end

class User < ActiveRecord::Base
  belongs_to :group
  has_many :meetings
end

class Room < ActiveRecord::Base
  belongs_to :group
  has_many :users, :through => :group
  has_many :meetings, :through => :users
  ...
end

If this is not the proper way to use has_many :through, is there a way 
to associate users meetings with the room?  Thanks for your help!

Chris

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