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Overview

Solidus's promotions system allows stores to give discounts to customers.

Promotions might be discounts on orders, line items, or shipping charges. The promotions system provides a set of handlers, rules, and actions that work together to provide flexible discounts in any scenario.

To account for all of the ways a discount may be applied, the promotions system has many complex moving parts.

We recommend that you start up a Solidus store on your local machine and see the built-in promotions functionality yourself, as store administrators have a flexible promotions system available by default (http://localhost:3000/admin/promotions). Here, administrators can add promotions and create complex strings of promotion rules and actions if necessary.

Promotion architecture

The following sections summarize the main parts of Solidus's promotions system.

Promotion model

The Spree::Promotion model defines essential information about a promotion. This includes the promotion's name, description, and whether the promotion should be active or not.

Take note of the following promotion attributes:

  • name: The name for the promotion. This is displayed to customers as an adjustment label when it is applied.
  • description: An administrative description for the promotion.
  • usage_limit: How many times the promotion can be used before becoming inactive.
  • starts_at and expires_at: Optional date values for the start and end of the promotion.
  • match_policy: When set to all, all promotion rules must be met in order for the promotion to be eligible. When set to any, just one of the promotion rules must be met.
  • path: If the promotion is activated when the customer visits a URL, this value is the path for the URL.
  • per_code_usage_limit: Specifies how many times each code can be used before it becomes inactive.
  • apply_automatically: If true, the promotion is activated and applied automatically once all of the eligibility checks have passed.

Note that you can access promotion information using the promotion method on its associated Spree::PromotionRule and Spree::PromotionAction objects:

Spree::PromotionAction.find(1).promotion

Promotion handlers

Subclasses of the Spree::PromotionHandler model activate a promotion if the promotion is eligible to be applied. There are Cart, Coupon, Page, and Shipping subclasses, each one used for a different promotion activation method. For more information, see the Promotion handlers article.

Once a promotion handler activates a promotion, and all of the eligibility checks pass, the Spree::PromotionAction can be applied to the applicable shipment, order, or line item.

Promotion rules

The Spree::PromotionRule model sets a rule that determines whether a promotion is eligible to be applied. Promotions may have no rules or many different rules.

By default, Spree::Promotions have a match_policy value of all, meaning that all of the promotion rules on a promotion must be met before the promotion is eligible. However, this can be changed to any.

An example of a typical promotion rule would be a minimum order total of $75 USD or that a specific product is in the cart at checkout.

For a list of available rule types and more information, see the Promotion rules article.

Promotion actions

The Spree::PromotionAction model defines an action that should occur if the promotion is activated and eligible to be applied. There can be multiple promotion actions on a promotion.

Typically, a promotion action could be free shipping or a fixed percentage discount.

A promotion action calculates the discount amount and creates a Spree::Adjustment for the promotion. The adjustment then adjusts the price of an order, line item, or shipment.

Promotion adjustments

Finally, the Spree::Adjustment model defines the discount amount that is applied. Each adjustment is created by a Spree::PromotionAction.

Every time that the promotion adjustment needs to be recalculated, the Spree::PromotionRules are re-checked to ensure the promotion is still eligible.

Note that shipments and taxes can also create adjustments. See the adjustments documentation for more information.

Eligibility

Spree::Promotion's performs a number of checks to determine whether a promotion is eligible to be applied:

  1. It checks that the promotion is active.
  2. It checks that the promotion usage limit has not been reached.
  3. It checks that the promotion code usage limit has not been reached.
  4. It checks that all of the products are promotable products.
  5. Finally, it checks the Spree::PromotionRules.

If all of these checks pass, then the promotion is eligible.

See the eligible? method defined in the Spree::Promotion model:

# models/spree/promotion.rb : line 123
def eligible?(promotable, promotion_code: nil)
  return false if inactive?
  return false if usage_limit_exceeded?
  return false if promotion_code && promotion_code.usage_limit_exceeded?
  return false if blacklisted?(promotable)
  !!eligible_rules(promotable, {})
end

Note that promotions without rules are eligible by default.

Once the promotion is confirmed eligible, the promotion can be activated through the relevant Spree::PromotionHandler.

Promotion flow

This section provides a high-level view of the promotion system in action. For the sake of this example, the store administrator is creating a free shipping promotion for orders over $100 USD.

  1. The administrator creates a Spree::Promotion from the Solidus backend.
  • They create a name, description, and optional category for the promotion.
  • They choose not to set a usage limit for the promotion.
  • They choose not to set a start or end date for the promotion.
  • They choose the "Apply to all orders" activation method. Alternatively, they could have chosen to apply promotions via a promotion code or a URL.
  1. The administrator creates Spree::PromotionRules for the promotion.
    • In this case, they use the rule type "Item Total" (Spree::Promotion::Rules::ItemTotal) and set the rule so that the order must be greater than $100 USD.
  2. The administrator creates Spree::PromotionActions for the promotion.
  • They use promotion action type "Free shipping", which uses the Spree::Promotion::Actions::Shipping model. In this case, the only available action is "Makes all shipments for the order free".
  • Because the promotion action requires a shipment, the Spree::PromotionHandler::Shipping will be used when it is time to activate the promotion.

Different types of promotions would change the customer's experience of promotion activation. For example, the customer might be required to enter a promotion code to activate some promotions, while another promotion could be applied automatically.

In this case, because the administrator used the "Apply to all orders" activation method, the promotion is applied automatically:

  1. The customer adds items to their cart. The Spree::Order total is greater than $100 USD.
  2. The customer begins the checkout process.
  3. The customer enters their shipping information.
  4. The Spree::PromotionHandler::Shipping handler checks that the Spree::PromotionRules are met. Because the order total is greater than $100 USD, the promotion is eligible.
  5. The Spree::PromotionHandler::Shipping activates the promotion.
  6. The Spree::PromotionAction associated with the promotion is computed and applied as a Spree::Adjustment that negates the order's shipping charges. The customer's shipping is now free.
  7. The customer completes the checkout process.