response for lets you decorate your actions respond_to blocks
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The gem is called response_for_rails

response_for (see ResponseFor::ActionController::ClassMethods) allows you to decorate the respond_to block of actions on subclassed controllers. This works nicely with

response_for's functionality can be summed up in one sentence:

“response_for allows you to specify default responses for any action (or before filter) that doesn't render or redirect”

Actions typically do two things - interact with models, and render a response. The above simple idea allows you to decouple these two functions (where appropriate), which means abstraction of common patterns becomes possible.

For Rails 3.0 and higher

Simply add the response_for_rails gem to your Gemfile

gem "response_for_rails"

Older rails

For Rails 2.2 thru 2.3

For these older versions of rails please checkout the 0.2-stable-rails2.1 branch. Plugin install on rails 2.2 and up can fetch from a branch.

./script/plugin install git:// -r 0.2-stable-rails2.1

For Rails 2.1

cd vendor/plugins
git clone git://
cd response_for
git checkout 0.2-stable-rails2.1
rmdir -f .git

For Rails 2.0

Please checkout the 0.1-stable-rails2.0 branch. Same general instructions for Rails 2.1 should work.

Run the specs

To get set up for development, do the following:

git clone git://
cd response_for
cp Gemfile.lock.development Gemfile.lock


class FooController < ApplicationController
  def index
    @foos = Foo.find(:all)
    # default response - render html

# this controller needs to respond_to fbml on index. 
# Using response_for, we don't need to repeat '@foos = Foo.find(1)'
class SpecialFooController < FooController
  response_for :index do |format|
    format.fbml { render :inline => turn_into_facebook(@foos) }



NOTE: 0.2-stable has BC-breaking API changes, and is supported only for Rails >= 2.1.x. Version 0.2.0 was released on Sept 14th 2008. You should use 0.1-stable in your existing projects until you have runs your specs and whatnot.

If you want to know more about why I changed the API in 0.2 read on

Why change the API in 0.2?

repsonse_for <= v0.1 intercepted respond_to calls to allow overriding of these by class level declarations. This turns out to have some headaches, such as:

  • If you have some bail-out code in before_filters which uses respond_to, then response_for tries to overwrite this. This meant that I had to write response_for to only kick in once before_filters had run. This made for some funky smelling code.

  • Sometimes your bail out code runs after the before_filters, in a superclass action for example, or just as part of your action (perhaps in another method). The above hack doesn't work for this case (the before_filters have run). The solution in this case was to use respond_to_without_response_for in any bail out code.

  • Conceptually, overriding code declared in methods, with code declared at the class level, is weird. Here's an example

    class FooController < SuperclassController
      response_for :index # override Superclass's index respond_to
      def index
        respond_to  # one might expect this to override the above, as its declared later - but it wont!

So, in 0.2 a much simpler idea is behind response_for - you can declare a default response for an action which will be performed if that that action has not already performed a render or redirect. This means that all of your bail out code written with respond_to will do what it's supposed to.

Rewriting for 0.2

If you're upgrading, you just need to convert any actions you want to override from this:

def index
  @things = Thing.all
  respond_to do |format|
    format.xml { render :xml => @things }

to this:

def index
  @things = Thing.all

response_for :index |format|
  format.xml { render :xml => @things }

Previous Versions: 0.1

There is a branch for rails 2.0 users on this release. If you are using rails 2.0, then you want the 0.1-stable-rails2.0 branch. If you are using rails >= 2.1 then use the 0.1-stable branch