has_many through help, what am I doing wrong?

My models are like this:

User
   has_and_belongs_to_many :Roles

Role
   has_and_belongs_to_many :Users

tables:

roles_users
   user_id
   role_id

roleGroups
   id
   role_id
   some_column

Now I want to create another association on the User model, that will be a collection of all roleGroups the user belongs to.

i.e. if the user is in roles with id's 1 and 2, then fetch all RoleGroups where role_id = 1 and 2.

I think I need to use a through because it is based on the user's Role association right?

I tried:

User
   has_many  :RoleGroups, :through => :Roles

Role
   has_many :RoleGroups, :through => :User

But 开发者_JAVA技巧I get an error saying:

ActiveRecord::HasManyThroughSourceAssociationMacroError: Invalid source reflection macro :has_many :through for has_many :RoleGroups, :through => :Roles.  Use :source to specify the source reflection.

Update Ok my models look like this now:

User
   habtm :Roles
   has_many :RoleGroups, :through => :Roles

Role
  habtm :Users
  has_many :RoleGroups

RoleGroup
  belongs_to :Role

mysql tables:

roles_users
   user_id
   role_id

role_groups
   id
   role_id
   col3
   col4
   ..

If I do:

u = User.find(1)
u.Roles  (works fine)
u.RoleGroups   #see error

Error message:

ActiveRecord::StatementInvalid: Mysql2::Error: Unknown column 'roles.user_id' in 'where clause': SELECT `role_groups`.* FROM `role_groups` INNER JOIN `roles` ON `role_groups`.role_id = `roles`.id WHERE ((`roles`.user_id = 1))

You're looking for the has_and_belongs_to_many association.

You can't do this the way you're thinking. I'm not sure why you're capitalizing your associations, but there are a few other things wrong, too.

First, RoleGroups hangs off of Role (via has_many, but more on that in a sec), which means you don't have a direct connection between User and RoleGroup.

Second, it appears from your updated explanation that each RoleGroup can have more than one Role, which is normal, but in your code Role has_many :role_groups, which means each role can have more than one role group. This is counterintuitive naming, but perhaps intentional. I'm going to assume that your role groups contain multiple roles rather than the other way around.

Third, you can't use a HABTM as a :through model. HABTM only uses a table in the database, not a Rails model, so the information in your roles_users table can't be used directly; has_many :foos :through => :bars requires an actual Bar model.

# Models
User
  habtm :roles

Role
  habtm :users
  belongs_to :role_group # add role.role_group_id attribute

RoleGroup
  has_many :roles # remove role_groups.role_id attribute

# Console
u = User.find(1) # get user
r = u.roles      # get user roles
u.roles.collect { |role| role.role_group.name } 
# ["Administrative","Editorial","User"]