RUby on Rails nested dynamic fields

Hi guys!

I have a problem to find the right way to program dynamic fields. For example: I have two radio buttons and depending on how the user selects one radio button, it extends the form with different fields.

Start form: - Radio button: car - Radio button: ship - Text field: name

If the user clicks on the radio button "car" the form gets extended with text fields like eg. "engine", "color" and if the user selects the radio button "ship" the form gets extended with text fields like "length", "weight". The attributes engine, color, length, weight are fields in the DB on table machine.

My problem is, what happens if the validation returns errors. How can i use partials to solve my problem. I have tried remote_function (to replace html parts), partials and rjs but rails returns me NameErrors!

My form looks like this:

<% form_for(@komplex_object, :url => some_url) do |f| %>
    <%= f.error_messages %> 
    <% f.fields_for :machine do |machine_f| %>
        <%= machine_f.radio_button :kind, 'car', :onclick => some_request_or_javascript, :checked => true -%> Car
        <%= machine_f.radio_button :kind, 'ship', :onclick => some_request_or_javascript -%> Ship       
        <div id="dynamic_fields">
            <% render :partial => 'car', :locals => { :f => machine_f } %>
        </div>
    <% end %>

    <p><%= f.label :name %>
    <%= f.text_field :name %></p>
    ...
<% end %>

Attention: the machine attributes are nested within the komplex_object form!

And here the partials:

# _car.html.erb
<p><%= f.label :engine %>
<%= f.text_field :engine %></p>
<p><%= f.label :color %>
<%= f.text_field :color %></p>

# _ship.html.erb
<p><%= f.label :length %>
<%= f.text_field :length %></p>
<p><%= f.label :weight %>
<%= f.text_field :weight %></p>

In the form i have write "some_request_or_javascript" and here I have test different solutions like javascript thats hides and shows two different div's that contains the car or ship fields. This solution runs but on submit sends all hash fields and not only these fields that the user have selected with the radio button. Second problem: how to recognise the right fields if submit returns validation errors?

Another solution is to use remote_function (that calls eg. check_fields) and partials (CODE POSTED ABOVE)! With this solutions i get NameErros on the rjs because the page.replace_html function

# controller function that remote function calls
# Ajax update for the right fields
def check_fields
  respond_to do |format|
          format.js { render :action => params[:kind] }
  end
end 

# ship.js.rjs
page.replace 'dynamic_fields', :partial => 'ship'

don't understand the "f" in the partial _ship.html.erb!

Any idea? thx in advance

ansaurus

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RUby on Rails nested dynamic fields

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