With Dependencies, you can easily replace parts of Spree core with your custom classes. You can replace Services, CanCanCan Abilities (user for Permissions), and API Serializers (used for generating JSON API responses).

We plan to expand this feature to include more classes in the future.

Application (global) customization

This will change every aspect of the application (both APIs, Admin Panel, and default Rails frontend if you’re using it).

In your config/initializers/spree.rb file, you can set the following:

Spree::Dependencies.cart_add_item_service = 'MyAddToCartService'


Spree.dependencies do |dependencies|
  dependencies.cart_add_item_service = 'MyAddToCartService'

Now let’s create your custom service.

mkdir app/services -f && touch app/services/my_add_to_cart_service.rb

And add the following code to it:

module MyAddToCartService < Spree::Cart::AddItem
  def call(order:, variant:, quantity: nil, public_metadata: {}, private_metadata: {}, options: {})
    ApplicationRecord.transaction do
      run :add_to_line_item
      run Spree::Dependencies.cart_recalculate_service.constantize
      run :send_notification


  def send_notification(new_order_line_item)


This code will:

  1. Inherit from Spree::Cart::AddItem
  2. Override the call method to add your custom logic
  3. Call run :add_to_line_item to add the item to the cart
  4. Call run Spree::Dependencies.cart_recalculate_service.constantize to recalculate the cart
  5. Call run :send_notification to send a notification

Values set in the initializer have to be strings, eg. 'MyNewAwesomeAddItemToCart'

Controller level customization

To replace serializers or Services in a specific API endpoint you can create a simple decorator:

Create a app/controllers/spree/cart_controller_decorator.rb

module Spree
  module CartControllerDecorator
    def resource_serializer

    def add_item_service


This will change the serializer in this API endpoint to MyNewAwesomeCartSerializer and also it will swap the default add_item_service to MyNewAwesomeAddItemToCart.

Different API endpoints can have different dependency injection points. You can review their source code to see what you can configure.

API level customization

Storefront and Platform APIs have separate Dependencies injection points so you can easily customize one without touching the other.

In your Spree initializer (config/initializers/spree.rb) please add:

Spree::Api::Dependencies.storefront_cart_serializer = 'MyNewAwesomeCartSerializer'
Spree::Api::Dependencies.storefront_cart_add_item_service = 'MyNewAwesomeAddItemToCart'

This will swap the default Cart serializer and Add Item to Cart service for your custom ones within all Storefront API endpoints that use those classes.

You can mix and match both global and API-level customizations:

Spree::Dependencies.cart_add_item_service = 'MyNewAwesomeAddItemToCart'
Spree::Api::Dependencies.storefront_cart_add_item_service = 'AnotherAddItemToCart'

The second line will have precedence over the first one, and the Storefront API will use AnotherAddItemToCart and the rest of the application will use MyNewAwesomeAddItemToCart

Default values

By default values can be easily checked by looking at the source code of Dependencies classes: