When you nest REST resources, ex: map.resources :articles do |article| article.resources :comments end
the scaffold_resource generated code has to be manually edited to add the parent id in about 15 locations accross 5 files of the child (the 4 views and the controller).
Most of the time, you must just replace comment_path(comment) by comment_path(@article, comment) , but - in new.rhtml you need to add a hidden field, and <%= f.hidden_field :article_id , :value => @article.id%>
- in the controller you also have to add a filter to fetch the parent before_filter :load_article def load_article @article= Article.find params[:article_id] end