Simple way to use Atom feed format in your Rails application [Part II of II]

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Simple way to use Atom feed format in your Rails application [Part II of II]


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How to use Atom feed format in your Rails application.

Click here if you just want to check the theory part.


In today's interconnected world, content distribution plays a vital role in keeping users engaged and informed. As a Rails developer, you're constantly seeking ways to deliver content seamlessly to your application's users.

One powerful solution that can revolutionize the way you share and distribute data is the Atom feed format. With its standardized structure and compatibility across platforms, Atom feeds provide a streamlined approach to content syndication.


In this article, we will delve into the world of Atom feeds and explore how you can effortlessly integrate them into your Rails application.


A "feed" refers to a format or mechanism used to distribute and deliver regularly updated content to users. It enables users to subscribe to and receive updates from websites, blogs, podcasts, or other online platforms in a standardized and structured manner.



Atom is a widely adopted XML-based feed format used for content syndication and distribution on the web. It is an open standard maintained by the Internet Engineering Task Force (IETF) and designed to provide a standardized format for publishing and subscribing to regularly updated content.


The following steps were applied in the following environment;

ruby 2.7.2p137
Deepin OS 20.7.1

Fetching the product

# app/controllers/products_controller.rb
def who_bought
    @product = Product.find(params[:id])
    @latest_order = @product.orders.order(:updated_at).last
    if stale?(@latest_order)
        respond_to do |format|

This action retrieves the orders associated with the @product instance variable and orders them by their updated_at timestamp in ascending order.

We check if @latest_order is considered stale. The stale? method is a built-in Rails method that helps in implementing HTTP caching and conditional GET request.

It helps determine whether the response should be re-rendered or if the client's cached version is still valid.

By adding format.atom, we cause Rails to look for a template named who_bought.atom.builder.

Create atom builder template

atom_feed do |feed|
  feed.title "Who bought #{@product.title}"

  feed.updated @latest_order.try(:updated_at) 

  @product.orders.each do |order|
    feed.entry(order) do |entry|
      entry.title "Order #{}"
      entry.summary type: 'xhtml' do |xhtml|
        xhtml.p "Shipped to #{order.address}"

        xhtml.table do
   'Total Price'
          order.line_items.each do |item|
     number_to_currency item.total_price
   'total', colspan: 2
   number_to_currency \

        xhtml.p "Paid by #{order.pay_type}"
      end do |author|

It is an Atom feed template written using the Builder syntax in a Rails view file (app/views/products/who_bought.atom.builder). It generates an Atom feed for the who_bought action in the ProductsController

This line atom_feed do |feed| initializes the Atom feed and provides a block with a feed object for further configuration.

This code generates an Atom feed that includes information about the product, the orders associated with it, and the details of each order such as shipping address, line items, total price, payment type, and author information.

Update relationships

This step is optional. It depends on your business logic.

Since I'm going to use @product.orders, it is necessary to have a direct relationship. In this case, I'm going to use the following snippet

# app/models/product.rb
  has_many :orders, through: :line_items

The class would be something like this

# app/models/product.rb
class Product < ApplicationRecord
  has_many :line_items
  has_many :orders, through: :line_items

By adding has_many :orders, through: :line_items, it establishes a direct association between the Product and Order models. It allows you to access the orders associated with a product by traversing through the line_items table.

For example, if you have a Product instance called product, you can access its associated orders using product.orders. This will return a collection of Order instances related to that specific product through the intermediate LineItem model.

This association simplifies querying and accessing orders associated with a product without explicitly referencing the LineItem model. It provides a convenient way to navigate the relationship between products and orders in your application.

This command through: :line_items specifies that the association between Product and Order is achieved through the line_items table or model. It indicates that there is an intermediate model (LineItem) that connects Product and Order indirectly.

Change routes

resources :products do
  get :who_bought, on: :member

The line get :who_bought, on: :member adds a custom route for the who_bought action to the products resource. It specifies that the route should be accessible on a member-level, meaning it will be a route that operates on a specific member (specific product) rather than the collection as a whole.

To be more specific, on: :member specifies that this route should be associated with a specific member (product) rather than the entire collection. It means the route will have a URL pattern that includes the product's identifier, such as /products/:id/who_bought.

Wrapping up, by including this route configuration, Rails will generate a route and corresponding URL helper methods for the who_bought action, allowing you to generate URLs and handle requests to /products/:id/who_bought. The :id parameter represents the identifier of the specific product.

For example, if you have a product with an ID of 2, you can access the who_bought action for that product using the URL /products/2/who_bought. This route would map to the appropriate controller and action, allowing you to handle and respond to requests made to that URL.

Test it

curl --silent http://localhost:3000/products/2/who_bought.atom

You should be able to see something like this

The command curl --silent http://localhost:3000/products/2/who\_bought.atom is a cURL command executed in a terminal. It makes a GET request to a local Rails application running on localhost at port 3000.

curl is a command-line tool used for making HTTP requests. When --silent (or -s) is used, it suppresses the progress output, making the command silent.

From the endpoint /products/2/who\_bought.atom, the command is requesting the Atom feed for the who_bought action of the ProductsController for the product with an id of 2.


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Final thoughts

I hope this article helped you. Let me know if you have any questions.

Your thoughts, suggestions and corrections are more than welcome.

By the way, feel free to drop your suggestions on new blog articles.

Hope to see you next time.