Rails 3 - Displaying submit errors on polymorphic comment model -

fairly new rails 3 , have been googling every way no avail solve following problem, tutorials stopping short of handling errors.

i have created rails 3 project multiple content types/models, such articles, blogs, etc. each content type has comments, stored in single comments table nested resource , polymorphic associations. there 1 action comments, 'create' action, because there no need show, etc belongs parent content type , should redisplay page on submit.

now have of working , comments submit , post fine, last remaining issue displaying errors when user doesn't fill out required field. if fields aren't filled out, should return parent page , display validation errors rails typically mvc.

the create action of comments controller looks this, , first tried...

def create    @commentable = find_commentable    @comment = @commentable.comments.build(params[:comment])     respond_to |format|       if @comment.save          format.html { redirect_to(@commentable, :notice => 'comment created.') }       else          format.html { redirect_to @commentable }          format.xml  { render :xml => @commentable.errors, :status => :unprocessable_entity }       end    end end  

when fill nothing out , submit comments form, page redirect it's appropriate parent, no flash or nothing displayed. figured out why, understand, flash won't persist on redirect_to, on render. here's trouble lies.

there 'create' action in comment controller, needed point render towards 'blogs/show' (note: know isn't polymorphic, once working i'll worry then). tried in "else" block of above code...

else    format.html { render 'blogs/show' }    format.xml  { render :xml => @commentable.errors, :status => :unprocessable_entity } end 

anyway, when try submit invalid comment on blog, error message saying "showing [...]/app/views/blogs/show.html.erb line #1 raised: undefined method `title' nil:nilclass."

looking @ url, think know why...instead of directing /blogs/the-title-of-my-article (i'm using friendly_id), it's going /blogs/the-title-of-my-article/comments. figure "comments" throwing query off , returning nil.

so how can page render without throwing 'comments' on there? or there better way go issue?

not sure if matters or helps, route.rb comments / blogs looks this...

resources :blogs, :only => [:show]    resources :comments, :only => [:create] end 

i've been plugging away @ on last few weeks , think i've pulled off, errors/proper direction on render, filled out fields remain filled in , all. did consider ajax, prefer graceful degradation if @ possible.

in addition, admit had go hacky-sack way, including pulling in way pluralize parent model render appropriate content type's show action, , @ stage need code work, not pretty doing it.

i know can refactored way better, , hope better rails. or, else thinks can improve welcomed have @ it. anyway, here code, wanted share , hope helps in same scenario.

comments_controller.rb

class commentscontroller < applicationcontroller     # include bring text helper methods controller     include actionview::helpers::texthelper      def create         @commentable = find_commentable         @comment = @commentable.comments.build(params[:comment])          respond_to |format|             if @comment.save                 format.html { redirect_to(@commentable, :notice => 'comment created.') }             else                  # transform class of commentable pluralized content type                 content_type = find_commentable.class.to_s.downcase.pluralize                  # choose appropriate instance variable based on @commentable, rendered page won't work without                 if content_type == 'blogs'                     @blog = @commentable                 elsif content_type == 'articles'                     @article = @commentable                 end                  format.html { render "#{content_type}/show" }                 format.xml  { render :xml => @commentable.errors, :status => :unprocessable_entity }             end         end     end       private      # gets id/type of parent model, see comment#create in controller     def find_commentable         params.each |name, value|             if name =~ /(.+)_id$/                 return $1.classify.constantize.find(value)             end         end     end end 

articles_controller.rb

class articlescontroller < applicationcontroller    def show     @article = article.where(:status => 1).find_by_cached_slug(params[:id])     @comment = comment.new      # on content type blogs_controller.rb, replace appropriate instance variable     @content = @article      respond_to |format|       format.html # show.html.erb       format.xml  { render :xml => @article }     end   end  end 

show.html.erb articles (change appropriate variables blog or whatever)

<h1><%= @article.title %></h1>  <%= @article.body.html_safe %>  <%= render :partial => 'shared/comments', :locals => { :commentable => @article } %> 

shared/_comments.html.erb (i'm leaving out displaying of posted comments here simplification, showing form submit them)

<%= form_for([commentable, @comment]) |f| %>     <h3>post new comment</h3>      <%= render :partial => 'shared/errors', :locals => { :content => @comment } %>        <div class="field">         <%= f.label :name, :value => params[:name] %>         <%= f.text_field :name, :class => 'textfield' %>     </div>      <div class="field">         <%= f.label :mail, :value => params[:mail] %>         <%= f.text_field :mail, :class => 'textfield'  %>     </div>      <div class="field">         <%= f.text_area :body, :rows => 10, :class => 'textarea full', :value => params[:body] %>     </div>      <%= f.submit :class => 'button blue' %> <% end %> 

shared/_errors.html.erb (i refactored partial reuse articles, blogs, comments, etc, standard error code)

<% if content.errors.any? %>     <div class="flash error">         <p><strong><%= pluralize(content.errors.count, "error") %> prohibited page being saved:</strong></p>         <ul>             <% content.errors.full_messages.each |msg| %>                 <li><%= msg %></li>             <% end %>         </ul>     </div> <% end %>