Rails - Feb 2007 - Q. re: Using models as join tables AND multiple models in forms

I read the section from AWDWR 2ed beginning at p. 337 about using a 
model to join tables.  I''m trying to combine this concept with having 
multiple models on one form.

Let''s say I have classes Account and Employee, with a many-to-many 
relationship between them.  I don''t want to use a pure join table 
because I want the AccountEmployee table to also contain a column for 
"role".  (Actually, I will name the join table
AccountEmployeeRelations)

I believe the model would look like this:

class Account < AR::Base
   has_many :account_employee_relations
   has_many :employees :through => :account_employee_relations
end

class Employee < AR::Base
   has_many :account_employee_relations
   has_many :accounts :through => :account_employee_relations
end

I assume I also need (but the book does not show):

class AccountEmployeeRelation < AR::Base
  belongs_to :accounts
  belongs_to :employees
end

In the migration for AccountEmployeeRelation I would guess I need lines 
like:
   t.column :account_id, :integer
   t.column :employee_id, :integer
   t.column :role, :string

The rest of my question probably depends on my interface.  I guess I 
could first create an account, and then on a separate form assign 
employees to that account.  I haven''t tried that, but I would expect 
that approach to be fairly easy.

But if I want to create the account and assign the employees in one 
form, I turn to p. 490 "Multiple Models in a Form".  Let''s
look at the
controller and view for edit/update (I might be able to figure out the 
rest once I have this part).

def edit
  @account = account.find(params[:id])
  @account_employee_relations = @account.employee_account_relations   # 
I think this is an array ?
end


# I haven''t worked on update yet since I can''t get edit to
work...but
I''m sure this won''t work.
def update
  @account = account.find(params[:id])
  if @account.update_attributes(params[:account])
    flash[:notice] = ''account was successfully updated.''
    redirect_to :action => ''show'', :id => @account
  else
    render :action => ''edit''
  end
end

I''m quite lost on this section of edit.rhtml:

<% form_for :account, @account, :url => { :action =>
"update", :id =>
@account } do |form| %>
...

<!-- I think I want to loop over all the assigned employees like this: -->
<% @account_employee_relations.each do |r| %>
<!-- Now I need a fields_for...over r ? -->
<% fields_for r do |f| %>
<tr>
   <th><label for="x">Employee:</label></th>
<!-- I want a selection box listing all the employees, with the 
currently assigned employee as the default selection -->
   <td><%= f.select(:employee_id, [array of names] %>  THIS DOES NOT
WORK!
   <label for="x">Role:</label>
   <%= f.select(:role, @account_employee_relation.possible_roles) 
%></td>   <!-- possible_roles is defined in the model -->
</tr>
<% end %>
<% end %>
...

Any help is appreciated!


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