---
title: render right
teaser: Thoughts on the `update` parameter in RJS.
tags: web,rails
author: Jared Carroll
published_on: 2007-07-30
---

One extension to Rails `ActionController::Base#render` method I don't like is
the new :update parameter.  This is used to render inline RJS in an action like:

```ruby
class CommentsController < ApplicationController

  def create
    @comment = Comment.new params[:comment]
    respond_to do |wants|
      if @comment.save
        wants.js do
          render :update do |page|
            page.insert_html :bottom, 'comments', render(:partial => 'comment',
                                                         :object => @comment)
            page[:errors].replace_html ''
            page[:comment_form].reset
          end
        end
      else
        wants.js do
          render :update do |page|
            page[:errors].replace_html @comment.errors.full_messages
          end
        end
      end
    end
  end

end
```

That's a very simple <abbr title="Asynchronous JavaScript And XML">AJAX</abbr>
comment submission.  Instead of creating RJS templates in `app/views/comments` I
just rendered the RJS inline in the action.  I think this is bad because:

1. look at how much longer the action is
1. the nesting makes it a pain to read
1. in this case the error display will be ugly because I can't call view methods
   such as `#error_messages_for` in a controller so I'm forced to call
   `ActiveRecord::Errors#full_messages`.

I think it's much better to use RJS views instead.  Then the above action becomes:

```ruby
class CommentsController < ApplicationController

  def create
    @comment = Comment.new params[:comment]
    respond_to do |wants|
      if @comment.save
        wants.js
      else
        wants.js { render :action => 'new.rjs' }
      end
    end
  end

end
```

In `create.rjs`:

```ruby
page.insert_html :bottom, 'comments', render(:partial => 'comment',
                                             :object => @comment)
page[:errors].replace_html ''
page[:comment_form].reset
```

In `new.rjs`:

```ruby
page[:errors].replace_html error_messages_for(:comment)
```

Then you say but it's only a couple lines of RJS, why create 2 more files just
for that?.  My answer would be: do you ever write normal non-AJAX actions like
this:

```ruby
class PostsController < ApplicationController

  def show
    @post = Post.find params[:id]
    html =<<-EOS
      <h2>#{@post.title}</h2>

      #{@post.body}
    EOS
    render :text => html, :layout => 'application'
  end

end
```

Of course not.

In my opinion, the :text and :update parameter options in
`ActionController#Base` should both be deprecated.