ruby on rails - Trying to show error messages, but running into: undefined method `errors' for nil:NilClass -

i trying implement error messages in rails , somehow fail work @ 1 point.

the view trying add error messages:

<%= form_for([@post, @post.comments.build], html: {class: 'form-horizontal'}) |f| %>              <% if @comment.errors.any? %>                  <div id="errorexplanation" class="span5 offset1 alert alert-error">                     <button type="button" class="close" data-dismiss="alert">&times;</button>                      <h4>something went wrong!</h4><br>                      <% @post.errors.full_messages.each |msg| %>                     <p><%= msg %></p>                     <% end %>                 </div>          <% end %> 

and controller:

def create @post = post.find(params[:post_id]) @comment = @post.comments.create(params[:comment].permit(:commenter, :body)) redirect_to post_path(@post) end 

and error message:

undefined method `errors' nil:nilclass extracted source (around line #65):

<li>             <%= form_for([@post, @post.comments.build], html: {class: 'form-horizontal'}) |f| %>  65 ->                       <% if @comment.errors.any? %>                      <div id="errorexplanation" class="span5 offset1 alert alert-error">                         <button type="button" class="close" data-dismiss="alert">&times;</button> 

the comments of course belong post can have many comments. help? tried think of (which not since new ror ;) - including various ways of trying error messages (@post.comment.errors.any? etc.).

thanks in advance. timo

from comments there many things going on here.

you're trying create comment, form action should commentscontroller#create. view makes sense postscontroller#show (you don't specify), , before rendering need instantiate @comment. possibly:

postscontroller

def show   @post = post.find(params[:id])   @comment = @post.comments.build end 

commentscontroller

def create   @post = post.find(params[:post_id])   @comment = @post.comments.build(params[:comment].permit(:commenter, :body))   if @comment.save     redirect_to post_path(@post)   else     render :file => "posts/show"   end  end 

note must render , not redirect keep hold of @comment instance , can render errors.

posts/show.html.erb

<%= form_for([@post, @post.comments.build], html: {class: 'form-horizontal'}) |f| %>     <% if @comment.errors.any? %> 

whether correct depend on routes.rb. i'm assuming comments nested resource in posts, question leads think.