Formtastic: how to choose what method to run on a collection to determine the label when using model associations?

Question

I have the following two simple models for users and user groups:

class User < ActiveRecord::Base
  belongs_to :user_group
end

and

class UserGroup < ActiveRecord::Base
  has_many :users
end

I use the following formtastic code to draw my form for the UserGroup model:

<% semantic_form_for [:system, @user_group] do |form| %>
  <% form.inputs do %>
    <%= form.input :name %>
    <%= form.input :description %>
    <%= form.input :users, :as => :check_boxes %>
  <% end %>
  <% form.buttons do %>
    <%= form.commit_button "Save Group" %>
  <% end %>
<% end %>

The form displays nicely and lists all Users in the system with checkbox checked for the users that currently belong to the UserGroup. Currently, the only attribute of the user in the list that it displays is the "username".

How is it determining to use the "username" method to get the label for each user?

How do I change it to show the "first_name" and "last_name" attributes?

Thanks

Answer 1

Looks like this is accomplished through formtastic's :label_method. Found in this answer.

<%= form.input :users, :label_method => :username, :as => :check_boxes %>

or

<%= form.input :users, :label_method => Proc.new { |x| "#{x.first_name} #{x.last_name}" }, :as => :check_boxes %>