Adding In Stock Notifications

A common feature of e-commerce stores is an email subscription to get notified when a product is back in stock. Now that we’ve seen the basics of Rails, let’s add this feature to our store.

Basic Inventory Tracking

First, let’s add an inventory count to the Product model so we can keep track of stock. We can generate this migration using the following command:

$ bin/rails generate migration AddInventoryCountToProducts inventory_count:integer

Then let’s run the migration.

$ bin/rails db:migrate

We’ll need to add the inventory count to the product form in app/views/products/_form.html.erb.

<%= form_with model: product do |form| %>
  <%# ... %>

  <div>
    <%= form.label :inventory_count, style: "display: block" %>
    <%= form.number_field :inventory_count %>
  </div>

  <div>
    <%= form.submit %>
  </div>
<% end %>

The controller also needs :inventory_count added to the permitted parameters.

    def product_params
      params.expect(product: [ :name, :description, :featured_image, :inventory_count ])
    end

It would also be helpful to validate that our inventory count is never a negative number, so let’s also add a validation for that in our model.

class Product < ApplicationRecord
  has_one_attached :featured_image
  has_rich_text :description

  validates :name, presence: true
  validates :inventory_count, numericality: { greater_than_or_equal_to: 0 }
end

With these changes, we can now update the inventory count of products in our store.