AJAX update of accepts_nested_attributes_for partials - ruby-on-rails

Question

My current working environment is Rails 2.3.8 (various reasons why my company hasn't moved to Rails 3).
I'm trying to update elements of a multi-model form via AJAX calls - the idea being to replace certain dropdowns depending on how the user selects or fills in other fields.
I have previously managed to get this working by using non-form based partials - the problem I have now is to reproduce the AJAX updating of the select dropdowns when the partials are based around form_for and fields_for.
Sorry for the following wall of text - i've tried to cut it down as much as possible (the code itself does work on my test site).
How do I generate the form builder elements in the Outbreak controller and then pass this to the category partial to take the place of incident_form?
Any pointers would be great :D
Models
class Outbreak < ActiveRecord::Base
has_many :incidents, :dependent => :destroy
has_many :locations, :through => :incidents
accepts_nested_attributes_for :locations, :allow_destroy => true, :reject_if => :all_blank
accepts_nested_attributes_for :incidents, :allow_destroy => true, :reject_if => :all_blank
end
class Incident < ActiveRecord::Base
belongs_to :outbreak
belongs_to :location
belongs_to :category
belongs_to :subcategory
belongs_to :subtype
end
class Location < ActiveRecord::Base
has_many :incidents, :dependent => :destroy
has_many :outbreaks, :thorugh => incidents
end
Views
_form
<% form_for(#outbreak, :html => {:multipart => true}) do |form| %>
<%= render :partial => 'outbreak_type_select', :locals => {:outbreak_types => #outbreak_types, :f => form } %>
<% form.fields_for :incidents do |incident_form| %>
<%= render :partial => 'category_select', :locals => {:categories => #categories, :incident_form => incident_form} %>
<%= render :partial => 'subcategory_select', :locals => { :subcategories => #subcategories, :incident_form => incident_form } %>
<% end %>
<% end %>
_outbreak_type_select
<% with_str = "'outbreak_type=' + value " %>
<% if #outbreak.id %>
<% with_str << "+ '&id=' + #{outbreak.id}" %>
<% end %>
<%= f.collection_select(:outbreak_type, #outbreak_types, :property_value, :property_value, {}, {:onchange => "#{remote_function(:url => { :action => "update_select_menus"}, :with => with_str)}"} ) %>
_category_select
After calling update_select_menus how to generate the incident_form
<%= incident_form.collection_select( :category_id, #categories, :id, :name, {:prompt => "Select a category"}, {:onchange => "#{remote_function(:url => { :action => "update_subcategory"}, :with => "'category_id='+value")}"}) %>
RJS
begin
page.replace_html 'outbreak_transmission_div', :partial => 'outbreaks/transmission_mode_select', :locals => {:transmission_modes => #transmission_modes }
rescue
page.insert_html :bottom, 'ajax_error', '<p>Error :: transmission modes update select</p>'
page.show 'ajax_error'
end
begin
page.replace_html 'incident_category_select', :partial => 'outbreaks/category_select', :locals => { :categories => #categories }
rescue
page.insert_html :bottom, 'ajax_error', '<p>Error :: incident category update select</p>'
page.show 'ajax_error'
end
Controllers
Outbreak
def new
#outbreak = Outbreak.new
#outbreak.incidents.build
#outbreak.locations.build
#just the contents for the dropdowns
#categories = Category.find(:all, :conditions => {:outbreak_type => "FOODBORNE"}, :order => "outbreak_type ASC")
#subcategories = Subcategory.find(:all, :order => "category_id ASC")
end
def update_select_menus
#outbreak_type = params[:outbreak_type].strip
if params[:id]
#outbreak = Outbreak.find(params[:id])
else
#outbreak = Outbreak.new
#outbreak.incidents.build
#outbreak.locations.build
end
if #outbreak_type == "FOODBORNE"
ob_type_query = "OUTBREAKS:TRANSMISSION_MODE:" << #outbreak_type
#transmission_modes = Property.find(:all, :conditions => {:field => ob_type_query})
ob_type_query = "INVESTIGATIONS:CATEGORY:" << #outbreak_type
#sample_types = Property.find(:all, :conditions => {:field => ob_type_query})
#categories = Category.find(:all, :conditions => { :outbreak_type => "FOODBORNE"})
#subcategories = Subcategory.find(:all, :conditions => { :category_id => #categories.first.id})
#subtypes = Subtype.find(:all, :conditions => { :subcategory_id => #subcategories.first.id})
elsif #outbreak_type == "NON-FOODBORNE"
ob_type_query = "OUTBREAKS:TRANSMISSION_MODE:" << #outbreak_type
#transmission_modes = Property.find(:all, :conditions => {:field => ob_type_query})
ob_type_query = "INVESTIGATIONS:CATEGORY:" << #outbreak_type
#sample_types = Property.find(:all, :conditions => {:field => ob_type_query})
#categories = Category.find(:all, :conditions => { :outbreak_type => "NON-FOODBORNE"})
#subcategories = Subcategory.find(:all, :conditions => { :category_id => #categories.first.id})
#subtypes = Subtype.find(:all, :conditions => { :subcategory_id => #subcategories.first.id})
end
respond_to do |format|
format.html
format.js
end
end

Answer 1

Found a work around based on http://www.treibstofff.de/2009/07/12/ruby-on-rails-23-nested-attributes-with-ajax-support/
This should probably go in Outbreak helper (in Outbreak controller atm)
def update_select_menus
#outbreak_type = params[:outbreak_type].strip
#next_child_index will only be used if
#next_child_index ? params[:next_child_index] : 0
if params[:id]
#outbreak = Outbreak.find(params[:id])
else
#outbreak = Outbreak.new
#outbreak.risks.build
#outbreak.incidents.build
#outbreak.locations.build
end
if #outbreak_type == "FOODBORNE"
ob_type_query = "OUTBREAKS:TRANSMISSION_MODE:" << #outbreak_type
#transmission_modes = Property.find(:all, :conditions => {:field => ob_type_query})
ob_type_query = "INVESTIGATIONS:CATEGORY:" << #outbreak_type
#sample_types = Property.find(:all, :conditions => {:field => ob_type_query})
#categories = Category.find(:all, :conditions => { :outbreak_type => "FOODBORNE"})
#subcategories = Subcategory.find(:all, :conditions => { :category_id => #categories.first.id})
#subtypes = Subtype.find(:all, :conditions => { :subcategory_id => #subcategories.first.id})
elsif #outbreak_type == "NON-FOODBORNE"
ob_type_query = "OUTBREAKS:TRANSMISSION_MODE:" << #outbreak_type
#transmission_modes = Property.find(:all, :conditions => {:field => ob_type_query})
ob_type_query = "INVESTIGATIONS:CATEGORY:" << #outbreak_type
#sample_types = Property.find(:all, :conditions => {:field => ob_type_query})
#categories = Category.find(:all, :conditions => { :outbreak_type => "NON-FOODBORNE"})
#subcategories = Subcategory.find(:all, :conditions => { :category_id => #categories.first.id})
#subtypes = Subtype.find(:all, :conditions => { :subcategory_id => #subcategories.first.id})
end
#pathogen_types = Property.find(:all, :conditions => {:field => "PATHOGENS:CATEGORY"})
#outbreak_types = Property.find(:all, :conditions => {:field => "OUTBREAKS:OUTBREAK_TYPE"} )
render :update do |page|
page.replace 'outbreak_transmission_div', :partial => 'transmission_mode_select_update'
page.replace 'incident_category_select', :partial => 'incident_category_select_update'
page.replace 'incident_subcategory_select', :partial => 'incident_subcategory_select_update'
page.replace 'incident_subtype_select', :partial => 'incident_subtype_select_update'
end
end
In the Outbreak view (although since this partial is related to Incident it should probably go in that view instead)
<% ActionView::Helpers::FormBuilder.new(:outbreak, #outbreak, #template, {}, proc{}).fields_for :incidents,{:child_index => #next_child_index} do |this_form| %>
<div id="incident_category_select">
<%= render :partial => 'category_select', :locals => {:incident_form => this_form } %>
</div>
<% end %>
The ActionView::Helpers::FormBuilder is used to produce the required fields_for form - The website article goes through this in more detail.
The resulting index is set by the #next_child_index variable which can be passed to the controller by the original AJAX call (for example #next_child_index = 1, then the resulting form element name will be outbreak [incidents_attributes] [1] [category_id] ) - I haven't used this in this example because although in future I want the form to support more than one location per Outbreak for this initial run-through it will just accept a single Location - Incident per Outbreak.
_category_select.erb partial (in Outbreak view atm)
<% with_str = "'category_id=' + value " %>
<% if #outbreak.id %>
<% with_str << "+ '&id=' + #{#outbreak.id}" %>
<% end %>
<%= incident_form.collection_select( :category_id, #categories, :id, :name, {:prompt => "Select a category"}, {:onchange => "#{remote_function(:url => { :action => "update_subcategory"}, :with => with_str)}"}) %>
The with_str is just to optionally pass the Outbreak id if it exists to the controller to find the Outbreak record to produce the form and if not to build a new Outbreak and associated nested attributes like Incidents and Locations.
The must be neater ways of doing this - especially the FormHelper and passing the Outbreak id via the optional with string.