render

List of status codes and their symbols

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

Using counters with collections

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.

Rendering nothing

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.

Custom collection local variable name

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

Streaming XML with Builder

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.

render_collection

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 %>

Optional local assigns

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 %>

:variable_name

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”

Rendering YAML

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.

RE: Using counters with collections

Note that as of Rails 2.1, it’s currently not possible to override the internal counter variable you get when using collections via passing it in through :locals.

This is a useful feature when you have a collection of items rendered but then wish to add another one - most likely via an AJAX request.

I’ve been informed it’s back in Edge, so hopefully it’ll re-appear again in Rails 2.2.

render with variables

perient view

Code example

<%= render 'time_select', locals: { select_name: 'from_tiem'}%>

render view

Code example

<%= locals[:select_name] %>

not:

Code example

<%= local_assigns[:select_name] %> 

Rendering JSONP

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]

Streaming Does Not Work with Mongrel

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.

Using render to handle ajax call using same js.erb(DRY)

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%>

Avoid DoubleRenderError

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.

typo

ActionController::Steaming => ActionController::Streaming