Ajax radio buttons. update the page div when a radio button is pressed.

<div id="join">
        <p class="title">
      Sign-up
        </p>
   <% form_for :radio_join, :html => { :id => 'radio_join' } do %>
      <%= radio_button_tag :join_page, :member %> Member
      <%= radio_button_tag :join_page, :model %> Model
      <%= radio_button_tag :join_page, :photographer %> Photographer
    <% end -%>
<% form_for :user, @user, :url => {:action => 'save_free'} do |user_form| -%>
        <div class="info">
    <%= render :partial => 'common/user_form', :object => user_form %>
                <p class="alignright">
        <%= submit_tag 'JOIN', :class => 'inputSubmit' %>
                </p>
      <br />
      <br />
        </div>
  <% end -%>

     </div>
<%= observe_form :radio_join, :url => { :action => 'choose_page' }, :update => "join", :complete => "Element.show('join')", :frequency => "0.25" %>

I frequently have to use methods such as 'radio_button' and 'check_box_tag' when I don't have an object with a method that will automatically determine the value of the input field. Therefore, I have to check to see if a certain parameter has been passed, and if so, if the parameter's value matches that of the input's value. This method does that.

It's designed to be used in a Rails helper. You can either pass it the object, method, and value (the same parameters as, for example, radio_button) or name and value (the same parameters as radio_button_tag).

def checked?( *args )
  if args.length == 3
    object, method, value = args
    if params[object] && params[object][method] && params[object][method] == value
      'checked'
    end
  elsif args.length == 2
    name, value = args
    if params[name] && params[name] == value
      true
    end
  end
end

Here's an example usage:

<%= radio_button 'person', 'age', '12', :checked => checked?( 'person', 'age', '12' ) %>

If params[:person][:age] exists and it equals '12', then 'checked?' returns 'checked'; otherwise, it returns nil.