Rails - Apr 2006 - Multiple Select example?

I''ve been trying to sort out a multiple select dropdown but
haven''t
found any good examples - anyone know of any or perhaps could make a
suggestion [see below]

Model:
1. Task AR has_many users
2. User AR belongs_to task
   login/password attributes

Controller:


View:
<%= collection_select("task", "users" , @users,
"id", "login", {},
{:multiple => true}) %>

 def new
   @task = Task.new
   @users = User.find_all
 end

 def create
   @task = Task.new(params[:task])

   if @task.save
     flash[:notice] = ''Task was successfully created.''
     redirect_to :action => ''list''
   else
     render :action => ''new''
   end
 end

Error:

"User expected, got String"


Seems pretty straight forward but isn''t working - any sugggestions?

Thanks.

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Found it!  FYI if it comes up again:

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Michael Koziarski wrote:
| Nice, are there any functions like this for handling one to many
| relations?  i.e a User has_and_belongs_to_many :groups.

collection_select requires a source object and an instance method.  With
has_many, this method can be the foreign key.  But with
has_and_belongs_to_many there is no corresponding instance method since
the keys are in a separate join table, so you''ll want to manage the
parameters yourself.  Here''s an example using
options_from_collection_for_select to create a multiple select:

class User < ActiveRecord::Base
~  # id, name fields
~  has_and_belongs_to_many :groups
end

class Group < ActiveRecord::Base
~  # id, name fields
~  has_and_belongs_to_many :users
end

class UserController < AbstractApplicationController
~  model :user
~  def edit
~    case @request.method
~    when :get
~      @user = User.find(@params[''id''])
~      @available_groups = Groups.find_all - @user.groups
~    when :post
~      @user =
User.find(@params[''user''][''id''])
~      @user.groups << Group.find(@params[''add_groups''])
~      redirect_to :action => ''show'', :id => @user.id
~    end
~  end
end

views/user/edit.rhtml
<%= form_tag :action => ''edit'' %>
~  <%= hidden_field ''user'', ''id'' %>
~  <select name="add_groups[]" multiple="multiple">
~    <%= options_from_collection_for_select @available_groups,
''id'',
''name'' %>
~  </select>
</form>


Check out the relevant FormOptionsHelper documentation:
http://ap.rubyonrails.org/classes/ActionView/Helpers/FormOptionsHelper.html#M000075

Best,
jeremy
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Actually - here''s my working sample [a little cleaner then above]

view:

   <select name="task[user_ids][]"
multiple="multiple">
     <%= options_from_collection_for_select @users, ''id'',
''login'' %>
   </select>

controller:

    @task = Task.new(@params[:task])


Turns out I missed this very valuable wiki entry - thanks Joel!

http://wiki.rubyonrails.com/rails/pages/HowtoUseFormOptionHelpers

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