Thanks,
Jay

Best regards,
Bill

_form.html.erb

<%= form.error_messages %>
<p>
  <%= form.label :title %><br />
  <%= form.text_field :title %>
</p>
<p>
  <%= form.label :due_date %><br />
  <%= form.datetime_select :due_date %>
</p>
<div id="tasks">
  <h3>Tasks</h3>
  <% form.fields_for :tasks do |task_form| -%>
    <%= render :partial => 'task', :locals => { :form => task_form }
%>
  <% end -%>
</div>
<%= add_task_link(form) %>
<p>
  <%= form.submit 'Save' %>
</p>

And here's the partial that gets called above (_task.html.erb)

<div class="task">
  <p>
    <%= form.label :name %>
    <%= form.text_field :name, :size => 15 %>
    <%= remove_task_link( form ) %>
  </p>
  <%= observe_field :project_tasks_attributes_0_name, :function =>
'alert("field changed")' %>
</div>

This doesn't work because I need to change the observe_field name
(:project_tasks_attributes_0_name) for each task.  If I had 3 tasks,
the
then the observe_field names would be:
:project_tasks_attributes_0_name
:project_tasks_attributes_1_name
:project_tasks_attributes_2_name

I was wondering if there is a way to access the index of the task form
loop to generate field names like the above.

Thanks,
Jay

On Aug 17, 9:35 pm, bill walton <bwalton...@gmail.com> wrote:

do |task_form|

could be replaced with

each_with_index |task_form, i|

both do and each take blocks. Probably won't work, but...

If you're sure of the naming / order, then the easiest way would be
something like (not tested)...

<% index = 0 %>
<% form.fields_for :tasks do |task_form| -%>
 <%= render :partial => 'task', :locals => { :form => task_form, :index => index } %>
  <% index += 1 %>
<% end -%>

And then in the partial, using a string instead of a symbol...

<%= observe_field "project_tasks_attributes_#{index}_name" ...

Not terribly rubyish, I know, but something on that order should be
workable ;-)

HTH,
Bill

I've just run into exactly the same problem, as I'm using jQuery to
build autocompleters and need the generated field id for my
observe_field call. I've looked all over for a way to access the
index, but couldn't find it anywhere. I decided to delve into the
Rails code and found a couple of helper methods in the
InstanceTagMethods moduke (http://github.com/rails/rails/blob/master/
actionpack/lib/action_view/helpers/form_helper.rb).

The methods of interest are santized_object_name and
sanitized_method_name. They take the FormHelper's object_name (which
is publically accessible) and return the generated form element id
(e.g. person[attributes][0][name] becomes person_attributes_0_name).
However, these methods are private to InstanceTagMethods, so you can't
get at them from within your fields_for block.

The solution I've used is to duplicate these methods in my
application_helper.rb, and call them from within my fields_for block:

# app/helpers/application_helper.rb
def sanitized_object_name(object_name)
  object_name.gsub(/\]\[|[^-a-zA-Z0-9:.]/,"_").sub(/_$/,"")
end

def sanitized_method_nam(method_name)
  method_name.sub(/\?$/, "")
end

def form_tag_id(object_name, method_name)
  "#{sanitized_object_name(object_name.to_s)}_#{sanitized_method_name
(method_name.to_s)}"
end

Then in my fields_for partial:

# app/views/people/_person_attributes.rb
# wrapped in person_form,fields_for :attributes do |attributes_form|
  <%= f.text_field :name %>
  <%= observe_field form_tag_id(f.object_name, :name), ... %>

This code works for index partials (i.e. those with absolute indexes)
and those generated with timestamp indexes (I'm using a customised
version of Ryan Bates' latest nested form code for Rails 2.3 -
http://github.com/ryanb/complex-form-examples). I'll post this code on
my site aswell.

Hope this helps! If anyone knows a better way to access the form
builder's index, please follow up this post!

Regards,
Chris
--
http://www.chrisblunt.com
http://twitter.com/cblunt

On Aug 17, 10:24 pm, Jay <jheas...@comcast.net> wrote: