gistfile1.rb

class User < ActiveRecord::Base
  attr_accessible :role_id, :as => :admin
  belongs_to :role
end

class Role < ActiveRecord::Base
  has_many :users
end

class UsersController < ApplicationController
  def update
    @user = User.find(params[:id])
    if @user.update_attributes(param[:user])
      #this stuff happens
    else
      # this stuff SHOULD happen.
    end
  end
end