Using render
You
can render the default view for a Rails template, or a specific template, or a file, or inline code, or nothing at all. You can render text, JSON,
or XML.
You can specify the content type or HTTP status
of the rendered response as well.
render :nothing => true
We see there is an empty response (no data after the Cache-Control line),
but the request was successful because Rails has set the response to 200 OK.
You can set the :status option
on render to change this response. Rendering nothing can be useful for AJAX requests
where all you want to send back to the browser is an acknowledgement that the request was completed.
instance variables that you require in the view must be set up in the current action before calling render.
render "/u/apps/warehouse_app/current/app/views/products/show"
By default, the file is rendered without using the current layout. If you want Rails to put the file into the current
layout, you need to add the :layout
=> true option.
render :inline => "<% products.each do |p| %><p><%= p.name %><p><% end %>"
render :inline =>
"xml.p {'Horrid coding practice!'}", :type => :builder
render :update do |page| page.replace_html 'warning', "Invalid options supplied" end
By default, if you use the :text option
the text is rendered without using the current layout. If you want Rails to put the text into the current layout, you need to add the:layout
=> true option.
Calls to the render method
generally accept four options:
:content_type :layout :status :location
render :status => 500 render :status => :forbidden
To assign a specific layout for the entire application, use a declaration in yourApplicationController class:
class ApplicationController < ActionController::Base layout "main" #... end
Choosing Layouts at Runtime
class ProductsController < ApplicationController
layout :products_layout
def show
@product = Product.find(params[:id])
end
private
def products_layout
@current_user.special? ? "special" : "products"
end
end
You can also decide the layout by passing a Proc object, the block you give the Proc will be given the controller instance,
so you can make decisions based on the current request. For example:
class ProductsController < ApplicationController
layout Proc.new { |controller| controller.request.xhr? ? 'popup' : 'application' }
end
Layouts are shared downwards in the hierarchy, and more specific layouts always override more general ones.
def show
@book = Book.find(params[:id])
if @book.special?
render :action => "special_show" and return
end
render :action => "regular_show"
end
Rails uses HTTP status
code 302 (temporary redirect) when you call redirect_to.
If you’d like to use a different status code (perhaps 301, permanent redirect), you can do so by using the :statusoption:
head :bad_request
head :created, :location => photo_path(@photo)
Structuring Layouts
Asset tags yield and content_for Partials
Asset Tags
auto_discovery_link_tag javascript_include_tag stylesheet_link_tag image_tag video_tag audio_tag
Using content_for and Understanding yield
<html> <head> <%= yield :head %> </head> <body> <%= yield %> </body> </html>
<% content_for :head do %> <title>A simple page</title> <% end %> <p>Hello, Rails!</p>
<html> <head> <title>A
simple page</title> </head>