Change instantiation method

lib/rails/form_helper.rb

@@ -1,42 +1,45 @@
 ActionView::Helpers::FormBuilder.class_eval do
-  
+
   def nested_fields_for(association, options={}, &block)
     raise ArgumentError, 'Missing block to nested_fields_for' unless block_given?
-    
+
     options[:new_item_index] ||= 'new_nested_item'
-    options[:new_object] ||= self.object.class.reflect_on_association(association).klass.new
+    unless options[:new_object]
+      options[:new_object] = self.object.send(association).build
+      self.object.send(association).destroy(options[:new_object])
+    end
     options[:item_template_class] ||= ['template', 'item', association.to_s.singularize].join(' ')
     options[:empty_template_class] ||= ['template', 'empty', association.to_s.singularize].join(' ')
     options[:show_empty] ||= false
     options[:render_template] = options.key?(:render_template) ? options[:render_template] : true
     options[:escape_template] = options.key?(:escape_template) ? options[:escape_template] : true
-    
+
     output = @template.capture { fields_for(association, &block) }
     output ||= template.raw ""
-    
+
     if options[:show_empty] and self.object.send(association).empty?
-      output.safe_concat @template.capture { yield nil } 
+      output.safe_concat @template.capture { yield nil }
     end
-    
+
     template = render_nested_fields_template(association, options, &block)
     if options[:render_template]
       output.safe_concat template
     else
       add_nested_fields_template(association, template)
     end
-    
+
     output
   end
 
 protected
-  
+
   def render_nested_fields_template(association, options, &block)
     templates = @template.content_tag(:script, :type => 'text/html', :class => options[:item_template_class]) do
       template = fields_for(association, options[:new_object], :child_index => options[:new_item_index], &block)
       template = AwesomeNestedFields.escape_html_tags(template) if options[:escape_template]
       template
     end
-    
+
     if options[:show_empty]
       empty_template = @template.content_tag(:script, :type => 'text/html', :class => options[:empty_template_class]) do
         template = @template.capture { yield nil }
@@ -45,17 +48,17 @@ def render_nested_fields_template(association, options, &block)
       end
       templates.safe_concat empty_template
     end
-    
+
     templates
   end
-  
+
   def add_nested_fields_template(association, template)
     # It must be a hash, so we don't get repeated templates on deeply nested models
     @template.instance_variable_set(:@nested_fields_template_cache, {}) unless @template.instance_variable_get(:@nested_fields_template_cache)
     @template.instance_variable_get(:@nested_fields_template_cache)[association] = template
     create_nested_fields_template_helper!
   end
-  
+
   def create_nested_fields_template_helper!
     def @template.nested_fields_templates
       @nested_fields_template_cache.reduce(ActiveSupport::SafeBuffer.new) do |buffer, entry|
@@ -64,5 +67,5 @@ def @template.nested_fields_templates
       end
     end unless @template.respond_to?(:nested_fields_templates)
   end
-  
+
 end