Rails - Oct 2007 - Best way to client-side load or hide state/province drop down when country is changed?

Maybe I''m just trying too hard, because I have done this plenty of
times with plain old javascript before Rails entered my life. But now
that I''m trying to work within the Rails system of form_for and such,
I am finding that what should be a simple task has become arduous
beyond compare. I''m ready to tear out what little hair I have left,
and I have yet to find anything online that addresses what I thought
would be a common scenario.

So, the scenario:
A user create/edit page. When a user selects US or Canada, the drop
down loads accordingly. If he selects a different country, the
dropdown disappears. When the form is submitted, the user and his
address are saved accordingly.

User: has_one :address
Address: has_one :state, has_one :country


edit.rhtml:
--------------
<% form_for :user, :url => {:action => "update", :id =>
@user} do |f|
%>
	<%= render :partial => "user_form", :locals => {:f => f}
%>
<% end %>

_user_form.rhtml:
--------------
First name: <%= f.text_field :first_name %><br />
Last name: <%= f.text_field :first_name %><br />
<% fields_for :address do |a| %><br />
   City: <%= a.text_field :city %><br />
   Country: <%= a.select :country_id, COUNTRIES %><br />
   State: <%= a.select :state_id, STATES %><br />
<% end %>

At first, I tried putting the state selector and text in its own
partial, thinking that via a custom onchange event on the country
selector and by using RJS I would be able to reload the state selector
from a controller method or hide it altogether. But in practice it
can''t be done because the state selector needs a form reference and
the controller can''t pass that in. It got ugly real fast.

So where I stand now, I''m looking at writing a custom javascript
method, fired from an onchange event on the country selector, that
would reload the contents of the state selector. Have I missed some
magical rails ingredient or helper that would make this better? Has it
just been too long a day? Any help appreciated.


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I got it working by foregoing a form_for selector for this attribute,
and using a manually loaded html selector instead. Seems to work as
desired, though it feels a bit hackish.


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i dont think that''s ''hackish''.
Basically you''re foregoing some automated magic for more control and
specificity
which in this case you needed.

On Oct 9, 11:22 pm, Yuval
<uberll...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> I got it working by foregoing a form_for selector for this attribute,
> and using a manually loaded html selector instead. Seems to work as
> desired, though it feels a bit hackish.

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True true! Just happy to get it working.

On Oct 10, 7:47 am, linoj
<lino...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> i dont think that''s ''hackish''.
> Basically you''re foregoing some automated magic for more control
and
> specificity
> which in this case you needed.
>
> On Oct 9, 11:22 pm, Yuval
<uberll...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>
> > I got it working by foregoing a form_for selector for this attribute,
> > and using a manually loaded html selector instead. Seems to work as
> > desired, though it feels a bit hackish.

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Yuval wrote:
> True true! Just happy to get it working.
yuval raz?
-- 
Posted via http://www.ruby-forum.com/.

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If you want a solution that is more Rails-centric...

First, I created some helper methods just for convenience.  (I only
needed the state_options one but created the others for testing this
solution).  The xxx_options simply creates an acceptable collection
for populating a Rails select.  The xxx_option_tags return a string of
option tags with the line breaks removed.  That''s necessary for their
inclusion in a js function below:

in application_helper.rb:
  ..
  def state_options
    Address::STATES.collect{|state| [state, state]}
  end

  def province_options
    Address::PROVINCES.collect{|state| [state, state]}
  end

  def state_option_tags
    options_for_select(state_options).gsub("\n", "")
  end

  def province_option_tags
    options_for_select(province_options).gsub("\n", "")
  end
  ...

I''ve got an address partial because I will capture addresses for all
kinds of different things (people, customers, businesses, etc).  My
address partial just consists of a normal ''fields_for
:address''.
Here''s the part relevant to the discussion:

    <%= f.select :state, state_options %>
    <%= f.text_field :postal_code %>
    <%= f.country_select :country, [''United States'',
''Canada''], :selected=>''United States''
%>
    <%= observe_field :address_country,
                      :function=> "switch(value){ case ''United
States'': $(''address_state'').show();$
(''address_state'').update(''#{state_option_tags}'');
break;  case
''Canada'': $(''address_state'').show();$
(''address_state'').update(''#{province_option_tags}'');
break; default: $
(''address_state'').hide();}" %>

Okay, so what''s going on...  I''m making use of the prototype
library
packaged with Rails and the baked-in "observe_field" helper.  This
helper observes the country select field and fires on a change (the
country select is rendered with US and Canada at the top before an
alphabetical listing of countries, and US is selected by default).
The :function=>... part is passing a js-function that will become the
method responsible for handling the change in the observe field.  It
will be wrapped in a function block that looks like: function(object,
value) {}.  That''s where the ''value'' field comes
from.  The rest of
the string is just a switch-statement that loads the appropriate
values into the select box or hides it all together.

The #{state_option_tag} is where the application_helper.rb comes into
play.  That is evaluated at run time to give the select options you
need.  The net effect is that the js swaps out the <option> tags in
the address_select field.

On Oct 9, 11:22 pm, Yuval
<uberll...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> I got it working by foregoing a form_for selector for this attribute,
> and using a manually loaded html selector instead. Seems to work as
> desired, though it feels a bit hackish.

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