Quantity parent options are updated through UJS

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');