Rails3: using Arel to make conditional searches based on conditional params

_search_form.html.erb

<div id="searchform">
  <%= form_tag search_people_path, :method => 'get' do |f| %>
    <div class="field">
      <%= label :search, :firstname, 'Firstname' %><br/>
      <%= text_field :search, :firstname %>
    </div>
    <div class="field">
      <%= label :search, :lastname, 'Lastname' %><br/>
      <%= text_field :search, :lastname %>
    </div>
    <%= submit_tag "Search" %>
  <% end %>
</div>

people_controller.rb

class PeopleController < ApplicationController
  # ... other CRUD actions ...
  def search
    q = Person.arel_table # initialize Arel table
    @people = Person.order(:created_at) # start with a simple option

    @search = Search.new(params[:search]) # initialize Search model with the search params
    # apply conditions only if they are present
    @people = @people.where(q[:lastname].matches("%#{@search.lastname}%")) if @search.lastname
    @people = @people.where(q[:firstname].matches("%#{@search.firstname}%")) if @search.firstname
    
    render :index # render index action, it's the same output, just filtered by conditions passed
  end
end

search.rb

# put this in app/models/search.rb
class Search
  attr_accessor :attributes
  
  def initialize(attributes = {})
    @attributes = attributes
    @attributes.each do |k,v| 
      self.class.send(:define_method,k) { v }
    end
  end
end