Rails 3 has adopted Unobtrusive Javascript and moved all the _remote functions to a plugin.   They did this in an effort to remove all the inline spaghetti code produced by the helpers and provide a more modular way to deal with Javascript & Ajax. I must admit I like the convenience of the old helpers, but its not really the best way to do things if you are dealing with a complex app that uses alot of Javascript.  So anyways, you will get the following error if you try to use the link_to_remote function:  undefined method ‘link_to_remote’

In order to use UJS in your Rails 3 app, you need to do the following:

1. Use the new javascript file, rails.js along with your favorite javascript framework

In your layout, you can use the default javascript tag to include this and prototype:
The only problem with this method is that it may add javascript files that you don’t need and this adds to page load time.  I like to take advantage of the Google hosted javascripts.  Most people already have them cached and chances are Google will serve the files faster than your hosting company.  I am using some of the scriptaculous libraries so I include that tag too.   Here is what I use:
Make sure you put the rails js tag after prototype.  I wasted 30 minutes figuring that out.

Rails 3 makes it easy to use jQuery or Mootools if you prefer them over Prototype.  Just include them instead.

2. Use the forgery protection meta tags: <%= csrf_meta_tag %>

Rails uses these to prevent XSS attacks.  I don’t know the details, so I will not go into it.. but you need to have this helper which spits out 2 meta tags:
Don’t hard code these.  The helper provides a unique token.

3. Change your link_to_remotes to link_to and use the :remote parameter

Lets say you have a list of widgets and people can vote Yes or No as to whether they like the widget.  After they vote, it updates the box with a highlight and changes the text to show you the vote result.  Here is my big ugly Rails 2 version of this:

Here is what you do in Rails 3  (please ignore the ugly path.. we are renovating):

You now use a regular link_to tag and pass the :remote parameter as true.

4. Use a js.erb file instead of render :text=>”blah blah”

The link_to tag does not accept :update, :complete, etc., like the link_to_remote tag did.  You can drop in a js.erb file to handle this stuff instead.  I determine the text and color of the highlight in my controller action. /myapp/app/views/widgets/vote.js.erb

Rails sends this back to your page and the javascript is executed.  This is a simplistic solution and the first one I found to produce the same behavior as my original Rails 2 helper.  There may be better ways to do this, but for now this works for me.  Here are some resources that I found useful when figuring this out:

Ryan Bates screencast was very helpful and most of this stuff was “inspired” from that.  Props Ryan, good stuff as usual -> http://railscasts.com/episodes/205-unobtrusive-javascript

Simone Carletti has a good overview on UJS in Rails 3, and is more geared towards jQuery – http://www.simonecarletti.com/blog/2010/06/unobtrusive-javascript-in-rails-3/

Another jQuery example – http://joshhuckabee.com/jquery-rails-3