Note that the :status option accepts not only an HTTP status code (such as 500), but also a symbol representing that code (such as +:created+), if that makes more sense to you. Here's a list of which symbols map to which numbers (derived from ActionController::StatusCodes::SYMBOL_TO_STATUS_CODE):

100 = :continue 101 = :switching_protocols 102 = :processing 200 = :ok 201 = :created 202 = :accepted 203 = :non_authoritative_information 204 = :no_content 205 = :reset_content 206 = :partial_content 207 = :multi_status 226 = :im_used 300 = :multiple_choices 301 = :moved_permanently 302 = :found 303 = :see_other 304 = :not_modified 305 = :use_proxy 307 = :temporary_redirect 400 = :bad_request 401 = :unauthorized 402 = :payment_required 403 = :forbidden 404 = :not_found 405 = :method_not_allowed 406 = :not_acceptable 407 = :proxy_authentication_required 408 = :request_timeout 409 = :conflict 410 = :gone 411 = :length_required 412 = :precondition_failed 413 = :request_entity_too_large 414 = :request_uri_too_long 415 = :unsupported_media_type 416 = :requested_range_not_satisfiable 417 = :expectation_failed 422 = :unprocessable_entity 423 = :locked 424 = :failed_dependency 426 = :upgrade_required 500 = :internal_server_error 501 = :not_implemented 502 = :bad_gateway 503 = :service_unavailable 504 = :gateway_timeout 505 = :http_version_not_supported 507 = :insufficient_storage 510 = :not_extended

When you're rendering a collection partial, the +partial_name_counter+ variable contains the position of the current element in the collection. For example:

<%= render(:partial => 'example', :collection => %w(rails-doc is cool)) %>

Now in _example.html.erb:

<p>Element: <%= example %> (index: <%= example_counter %>)</p>

It would produce:

<p>Element: rails-doc (index: 1)</p>
<p>Element: is (index: 2)</p>
<p>Element: cool (index: 3)</p>

As you can see, indexing starts from 1.

If your controller action does not explicitly call render, Rails will, by default, attempt to locate and render the template corresponding to the action. It's not uncommon, for example with Ajax calls, to want to render nothing. This will circumvent the default rendering and prevent errors on missing templates. To render nothing simply do the following:

render :nothing => true

Its important to note that this isn't the same as returning no HTTP response. In fact, this results in an HTTP response with a status code of 200 OK being sent back with a blank content body. Why does it matter? Well, you can still test your controller by asserting that a :success response was returned.

Regarding the previous note from hoodow about using :variable_name to create a custom local variable name when rendering a collection with a partial, the argument should be :as instead of :variable_name, so:

render :partial => "video_listing", :collection => @recommendations, :as => :video

You can wrap render in helpers. For example, render_collection. In app/helpers/application.rb:

module ApplicationHelper
def render_collection(name, collection)
  render :partial => "shared/#{name}", :collection => collection
end
end

In views:

<h2>Comments</h2>
<%= render_collection :comments, @photo.comments %>

When you have a partial with optional local assigns, for instance:

<%= render :partial => 'articles/preview' %>
<%= render :partial => 'articles/preview', :locals => { :show_call_out => true } %>

And you don't want the partial to break when the local isn't assigned, you can reference it through the +local_assigns+ local variable instead of through the template binding:

<% if local_assigns[:show_call_out] %>
<em><%= format @article.call_out %></em>
<% end %>

To generate larger XMLs, it's a good idea to a) stream the XML and b) use Active Record batch finders.

Here's one way of doing it:

def my_action
@items = Enumerable::Enumerator.new(
  Item.some_named_scope,
  :find_each,
  :batch_size => 500)

respond_to do |format|
  format.xml do
    render :text => lambda { |response, output|
      extend ApplicationHelper

      xml = Builder::XmlMarkup.new(
        :target => StreamingOutputWrapper.new(output),
        :indent => 2)
      eval(default_template.source, binding, default_template.path)
    }
  end
end
end

The Builder template does not need to be modified.

In Edge Rails you can do something like this to change the local variable name when rendering a collection:

render :partial => "video_listing", :collection => @recommendations, :variable_name => "video"

When you want to render XML or YAML you can use render :xml, some_object.to_xml or render :json, some_object.to_json

However there is no equivalent for YAML. What you can do is render just plain text with a correct content-type: render :text => some_object.to_yaml, :content_type => 'text/yaml'

The content_type is debatable but this seems to be the most standard.

If you are trying to stream output via render :text => Proc and Mongrel, be sure to note that this does NOT work. Mongrel returns a StringIO, which by nature buffers everything.

Unsure of how to actually stream output with Rails in a consistent fashion.

One can not invoke render twice during an action. Thus if You have a complicated rendering logic but at the end would like to render some default content, or just would like to find out whether render has been called during the current action, use performed?. This also works with "empty" renderings such as head.

ActionController::Steaming => ActionController::Streaming

If you provide the :callback option with a nil value, then the default JSON object will be returned. As such, this makes creating JSONP response from the render syntax very easy in your controllers, like so:

render json: @object, callback: params[:jsoncallback]

Suppose your application have many pages using some common view and is updated using ajax,so you can use a single js in multiple views to avoid duplication

format.js { render 'profile/show_user_details' } And in my profiles/show_user_details.js i can use conditions instead of creating regular partials

<% if params[:controller]== "dashboard"%>

$("admin_panel").show(); $("user_panel").hide(); <% elsif params[:controller]== "user"%> $("admin_panel").hide(); $("user_panel").show(); <% elsif params[:controller]== "video"%> $("admin_panel").hide(); $("user_panel").hide(); $("video_panel").show(); <% else %> $("admin_panel").hide(); $("user_panel").hide(); $("video_panel").hide(); <%end%>