gistfile1.rb

class User < ActiveRecord::Base
  scope :order, lambda{|params|
    return if params.nil?
    order = []
    params.split(/\|/).each do |param|
      order << param.gsub(/_asc/, ' ASC').gsub(/_desc/, ' DESC')
    end
    {:order => order.join(' ,')}
  }
end

module UsersHelper
  def order(attribute)
    order_first = "#{attribute.to_s}_asc"
    order_rest  = []
    if params[:order].present?
      params[:order].split(/\|/).each do |param|
        param.match(/(\w+)_(asc|desc)/) do |match_data|
          if match_data[1] == attribute.to_s
            order_first = "#{attribute.to_s}_#{reverse(match_data[2])}"
          else
            order_rest << param
          end
        end
      end
    end
    {:order => order_rest.unshift(order_first).join('|'), :page => params[:page], :per_page => params[:per_page]}
  end
  
  def reverse(order)
    case order
    when 'asc'
      'desc'
    when 'desc'
      'asc'
    else
      'asc'
    end
  end
end

    <th><%= link_to 'name', users_path(order(:name)) %></th>
    <th><%= link_to 'email', users_path(order(:email)) %></th>