Error messages for nested resource; guide says to use f.error_messages, but is deprecated/didn't work.

rubyonrails-talk
1

I've been trying to set up a new Rails 3 project as per Getting Started with Rails — Ruby on Rails Guides, but I'm running into difficulty with displaying errors when adding a new comment. The comments are a nested resource of posts. On the posts/show page, I have

<%= form_for([@post, @post.comments.build]) do |f| %>   <%= f.error_messages %>

  <div class="field">     <%= f.label :commenter %><br />     <%= f.text_field :commenter %>   </div>   <div class="field">     <%= f.label :body %><br />     <%= f.text_area :body %>   </div>   <div class="actions">     <%= f.submit %>   </div> <% end %>

But the f.error_messages is deprecated. I've read online that one solution is to use a partial and pass in the offending object as a target to it, but I don't know how to reference the comments object. It would look something like

<%= form_for([@post, @post.comments.build]) do |f| %> <%= render"shared/error_messages", :target => @comment %> … <% end %>

where @comment is the comment object. The examples online don't show how to do it when you pass an array to form_for. How can I get the error messages to show up for new comments?

For reference, the CommentsController looks like:

class CommentsController < ApplicationController   def create     @post = Post.find(params[:post_id])     @comment = @post.comments.create(params[:comment])     redirect_to post_path(@post)   end end

and the Comment model looks like:

class Comment < ActiveRecord::Base   validates :commenter, :presence => true   validates :body, :presence => true   belongs_to :post end

2

You want to set your comment variable in the controller:

def new   @comment = @post.comments.build end

so your form is

<%= form_for([@post, @comment]) do |f| %> <%= render"shared/error_messages", :target => @comment %> <% end %>

If you build the comment in the form (which you shouldn't be doing anyways if you're sticking to MVC principles), then when you render the form, a new comment object is always created. Since it's a new object, it won't have any errors.