Ruby on Rails with text_field_with_auto_complete

I spent some time trying to figure out how to get a little text field with auto complete in Rails. Now I wanted many fields to have the same suggestions in one form. So here are some code samples. For some information. I have a model that is called Locations, basically this is just a collection of names of cities a person should be able to travel to.
In my controller I need

# The first value is the model the second the name of the field

  auto_complete_for :location, :name
  
  # As of rails version > 2.0 forgery protection is activated by default. As the
  # AJAX stuff won't work otherwise you have to disable it for one method

  protect_from_forgery :except => [:auto_complete_for_location_name]

  # This is the method called my the AJAX obj
  def auto_complete_for_location_name
    leg= params[:location].keys[0] # get index as its always only one at a time

    auto_complete_responder_for_name params[:location][leg][:name]
  end
 
  # This does the real magic. It queries the database and then renders a 
  # partial 'names' with the list of values to display. With some sql knowledge 

  # you should be able to understand the query
   private
  def auto_complete_responder_for_name(value)
    param= '%' + value.downcase + '%' 
    find_options= {
      :conditions => [ 'LOWER(name) LIKE ?', param ],
      :order => 'name ASC',
      :limit => 10
    }
    @names = Location.find(:all, find_options)
    render :partial => 'names'

  end

So that is for the controller. Now we need to create the partial. You can call this what ever you want but for now I called it names. So you need a file named '_names'

<ul class="autocomplete_list">
  <% for name in @names -%> 
    <li class="autocomplete_item"><%= name.name %> </li>
  <% end -%>
</ul>

This is quite simple it get's the array @names we built in the controller and builds an unordered list out of the elements.

Next we have to add a little helper method to the app/helpers/application_helper.rb file. This is basically the wrapper for the 'real' auto_complete_field.

# Methods added to this helper will be available to all templates in the application.

module ApplicationHelper
  
  def my_text_field_with_auto_complete(object, method, tag_options = {}, completion_options = {})
    if(tag_options[:index])
      tag_name = "#{object}_#{tag_options[:index]}_#{method}"

    else
      tag_name = "#{object}_#{method}"
    end

    (completion_options[:skip_style] ? "" : auto_complete_stylesheet) +
      text_field(object, method, tag_options) +
      content_tag("div", "", :id => tag_name + "_auto_complete", :class => "auto_complete") +
      auto_complete_field(tag_name, { :url => { :action => "auto_complete_for_#{object}_#{method}" } }.update(completion_options))
  end

end

So now we should have everything that is needed to create our little textbox. Now in the view you just add

<%= my_text_field_with_auto_complete :location, :name, {:index => '1'} %>

And you increment the index value for every new field you add in that view.

Thank you to Wolfmans Howlings for posting all this.
http://blog.wolfman.com/articles/2006/10/17/having-multiple-text_field_with_auto_complete-in-the-same-view
http://wiki.rubyonrails.org/rails/pages/How+to+use+text_field_with_auto_complete