Where to render comments controller in Rails on model validations failure?

Question

I have a simple Video model in my rails app that has_many comments. I am displaying these comments on the video's show page. When I submit the form everything works fine; however, if there are validation errors on the Comment model, then my system blows up. If there are validation errors on the Comment model, I would simply like to render the video's show page again, with the validation error styling showing. How do I do this inside of my create action? Thanks a lot!

class CommentsController < ApplicationController
  def create
    @video = Video.find(params[:video_id])
    @comment = @video.comments.build(params[:comment])
    if @comment.save
      redirect_to @video, :notice => 'Thanks for posting your comments.'
    else
      render # what? What do I render in order to show the video page's show action with the validation error styling showing? Please help!
    end
  end
end

Answer 1

To do this you'll have to render a template:

class CommentsController < ApplicationController
  def create
    @video = Video.find(params[:video_id])
    @comment = @video.comments.build(params[:comment])
    if @comment.save
      redirect_to @video, :notice => 'Thanks for posting your comments.'
    else
      render :template => 'videos/show'
    end
  end
end

Keep in mind that you'll have to declare any instance variables (like @video) inside of the CommentsController#create action as well though, because the VideosController#show action will not be run, the template will simply be rendered. For instance, if you have an @video_name variable in your VideosController#show action, you'll have to add the same @video_name instance variable to the CommentsController#create action.