Quantity parent options are updated through UJS

app/controllers/quantities_controller.rb

@@ -1,6 +1,6 @@
 class QuantitiesController < ApplicationController
   before_action :init_session_filters
-  before_action :find_project_by_project_id, only: [:index, :create, :filter]
+  before_action :find_project_by_project_id, only: [:index, :parents, :create, :filter]
   before_action :find_quantity, only: [:edit, :update, :destroy, :toggle, :move]
   before_action :authorize
 
@@ -10,6 +10,11 @@ class QuantitiesController < ApplicationController
     prepare_quantities
   end
 
+  def parents
+    @form = params[:form]
+    @domain = params[:quantity][:domain]
+  end
+
   def create
     @quantity = @project.quantities.new(quantity_params)
     if @quantity.save

app/views/quantities/_form.html.erb

@@ -1,35 +1,16 @@
 <%= error_messages_for @quantity %>
 
 <div class="box tabular">
-  <p><%= f.select :domain, domain_options, {required: true} %></p>
-  <% Quantity.domains.each_key do |d| %>
-    <div id="parent_select_<%= d %>" <%= 'style=display:none;' if @quantity.domain != d %>>
-      <p><%= f.select :parent_id, parent_options(d), {required: true,
-                                                      label: :field_parent_quantity,
-                                                      include_blank: t('.null_parent')} %></p>
-    </div>
-  <% end %>
+  <p><%= f.select :domain, domain_options, {required: true}, data: {
+    remote: true,
+    url: parents_project_quantities_path(@project),
+    params: "form=#{f.options[:html][:id]}"
+  } %></p>
+  <p><%= f.select :parent_id, parent_options(@quantity.domain),
+    {required: true, label: :field_parent_quantity, include_blank: t('.null_parent')} %></p>
   <p><%= f.text_field :name, size: 25, required: true %></p>
   <p><%= f.text_field :description, style: "width: 100%;" %></p>
   <p><%= f.text_field :formula, placeholder: t('.formula_placeholder'),
       style: "width: 100%;" %></p>
   <p><%= f.check_box :primary %></p>
 </div>
-
-<%= javascript_tag do %>
-  function domainChange() {
-    box = $(this).closest('div');
-    box.find('[id^=parent_select_]').prop('disabled', true).hide();
-    box.find('[id^=parent_select_] select').attr('name', 'placeholder');
-    domain = $(this).val();
-    box.find('[id=parent_select_'+domain+']').prop('disabled', false).show();
-    box.find('[id=parent_select_'+domain+'] select')
-      .attr('name', 'quantity[parent_id]');
-  }
-  $('form').on('change', '#quantity_domain', domainChange);
-
-  //Firefox does not emit 'change' signal when preserving form over reload
-  $(document).ready(function() {
-    domainChange();
-  });
-<% end %>

app/views/quantities/parents.js.erb

@@ -0,0 +1,5 @@
+$('<%= "##{@form} " if @form %>#quantity_parent_id').empty().append(
+  '<%= escape_javascript(options_for_select(
+    parent_options(@domain).unshift([t('quantities.form.null_parent'), nil])
+  )) %>'
+);

app/views/quantities/toggle.js.erb

@@ -1,3 +1,4 @@
 $('div[id^=flash_]').remove();
 $('#content').prepend('<%= escape_javascript(render_flash_messages) %>');
 $('#quantities').html('<%= escape_javascript(render :partial => 'quantities/index') %>');
+$('#quantity_domain').trigger('change');

config/routes.rb

@@ -25,7 +25,10 @@ resources :projects do
         post 'toggle'
         post 'move/:direction', to: 'quantities#move', as: :move
       end
-      get 'filter', on: :collection
+      collection do
+        get 'parents'
+        get 'filter'
+      end
     end
     resources :units, :only => [:index, :create, :destroy]
   end

init.rb

@@ -19,7 +19,7 @@ Redmine::Plugin.register :body_tracking do
       :measurements => [:index],
       :ingredients => [:index, :nutrients, :filter, :filter_nutrients],
       :sources => [:index],
-      :quantities => [:index, :filter],
+      :quantities => [:index, :parents, :filter],
       :units => [:index],
     }, read: true
     permission :manage_common, {