[Rails] Associations

["Luis G. Gómez"]

Hello again...

The idea behind this app is to be able to serve certail files to certain 
users. To assign files to users you can create a group and add users and 
files and/or explicitly assign or exclude files for a particular user.

So, I grab the user's id at login. I fetch the groups to which the user 
belongs to in order to find the files he/she has access to. After I know 
which files the user has access to based on the groups, I check for 
entries in the documents_users table. Entries in documents_users have a 
flag (documents_users.switch) that is eithar 0 or 1 based on which I add 
or remove files from the users accessible file list (0=remove and 
1=add). At the end I just render the list of files so the use can 
download it. The rendering part is done, what I don't get are the files. 
I can't find a way to have the view render @user.documents based on the 
described criteria.

Here are my model deffinitions (table deffinitions are bellow):

User Model
       1 require 'active_record'
       2
       3 class User < ActiveRecord::Base
       4         has_and_belongs_to_many :documents, :conditions => 
"switch=1"
       5         has_and_belongs_to_many :groups
       6         def self.authenticate(name,password)
       7                 find_first(["alias='%s' AND 
password='%s'",name,password])
       8         end
       9 end

Group Model
       1 require 'active_record'
       2
       3 class Group < ActiveRecord::Base
       4         has_many :users
       5         has_many :documents
       6 end

Document Model
       1 require 'active_record'
       2
       3 class Document < ActiveRecord::Base
       4         has_and_belongs_to_many :users
       5         has_and_belongs_to_many :groups
       6         def self.user_documents(user)
       7                 find_by_sql("SELECT * FROM groups WHERE 
name='#{user}'")
       8         end
       9 end


//////////TABLES//////////
CREATE TABLE `documents` (
   `id` int(11) NOT NULL auto_increment,
   `name` varchar(100) NOT NULL default '',
   `size` float NOT NULL default '0',
   `last_mod` timestamp NOT NULL,
   `mime` varchar(100) NOT NULL default '',
   `document` blob NOT NULL,
   PRIMARY KEY  (`id`)
) TYPE=MyISAM DEFAULT CHARSET=latin1;

CREATE TABLE `documents_groups` (
   `group_id` int(11) NOT NULL default '0',
   `document_id` int(11) NOT NULL default '0',
   PRIMARY KEY  (`group_id`,`document_id`)
) TYPE=MyISAM DEFAULT CHARSET=latin1;

CREATE TABLE `documents_users` (
   `document_id` int(11) NOT NULL default '0',
   `user_id` int(11) NOT NULL default '0',
   `switch` tinyint(4) NOT NULL default '0',
   PRIMARY KEY  (`document_id`,`user_id`)
) TYPE=MyISAM DEFAULT CHARSET=latin1;

CREATE TABLE `groups` (
   `id` int(11) NOT NULL auto_increment,
   `name` varchar(100) NOT NULL default '',
   PRIMARY KEY  (`id`),
   KEY `group_name` (`name`)
) TYPE=MyISAM DEFAULT CHARSET=latin1;

CREATE TABLE `groups_users` (
   `switch` tinyint(4) NOT NULL default '0',
   `group_id` int(11) NOT NULL default '0',
   `user_id` int(11) NOT NULL default '0',
   PRIMARY KEY  (`group_id`,`user_id`)
) TYPE=MyISAM DEFAULT CHARSET=latin1;

CREATE TABLE `users` (
   `admin` tinyint(1) NOT NULL default '0',
   `id` int(11) NOT NULL auto_increment,
   `alias` varchar(100) NOT NULL default '',
   `password` varchar(100) NOT NULL default '',
   PRIMARY KEY  (`id`),
   UNIQUE KEY `user` (`alias`)
) TYPE=MyISAM DEFAULT CHARSET=latin1;
//////////ENDTABLES//////////

Arent the has_and_belongs_to_many associations supposed to unse a 
relationship table to perform joins? In this case tables 
documents_groups, documents_users and groups_users.

Hope you see what I'm missing... :S

Thank you!!

LG