CRUD Actions

We need to be able to access individual products. This is the R in CRUD to read a resource.

We’ve already defined the route for individual products with our resources :products route. This generates /products/:id as a route that points to products#show.

Now we need to add that action to the ProductsController and define what happens when it is called.

Open the Products controller and add the show action like this:

class ProductsController < ApplicationController
  def index
    @products = Product.all
  end

  def show
    @product = Product.find(params[:id])
  end
end

The show action here defines the singular @product because it’s loading a single record from the database, in other words: Show this one product. We use plural @products in index because we’re loading multiple products.

To query the database, we use params to access the request parameters. In this case, we’re using the :id from our route /products/:id. When we visit /products/1, the params hash contains {id: 1} which results in our show action calling Product.find(1) to load Product with ID of 1 from the database.

We need a view for the show action next. Following the Rails naming conventions, the ProductsController expects views in app/views in a subfolder named products.

The show action expects a file in app/views/products/show.html.erb. Let’s create that file in our editor and add the following contents:

<h1><%= @product.name %></h1>

<%= link_to "Back", products_path %>

It would be helpful for the index page to link to the show page for each product so we can click on them to navigate. We can update the app/views/products/index.html.erb view to link to this new page to use an anchor tag to the path for the show action.

<h1>Products</h1>

<div id="products">
  <% @products.each do |product| %>
    <div>
      <a href="/products/<%= product.id %>">
        <%= product.name %>
      </a>
    </div>
  <% end %>
</div>

Refresh this page in your browser and you’ll see that this works, but we can do better.

Rails provides helper methods for generating paths and URLs. When you run bin/rails routes, you’ll see the Prefix column. This prefix matches the helpers you can use for generating URLs with Ruby code.

                                  Prefix Verb   URI Pattern                                                                                       Controller#Action
                                products GET    /products(.:format)                                                                               products#index
                                 product GET    /products/:id(.:format)                                                                           products#show

These route prefixes give us helpers like the following:

• products_path generates "/products"
• products_url generates "http://localhost:3000/products"
• product_path(1) generates "/products/1"
• product_url(1) generates "http://localhost:3000/products/1"

_path returns a relative path which the browser understands is for the current domain.

_url returns a full URL including the protocol, host, and port.

URL helpers are useful for rendering emails that will be viewed outside of the browser.

Combined with the link_to helper, we can generate anchor tags and use the URL helper to do this cleanly in Ruby. link_to accepts the display content for the link (product.name) and the path or URL to link to for the href attribute (product).

Let’s refactor this to use these helpers:

<h1>Products</h1>

<div id="products">
  <% @products.each do |product| %>
    <div>
      <%= link_to product.name, product_path(product.id) %>
    </div>
  <% end %>
</div>