class-extension-points.md

Class extension points

The Spree::AppConfiguration object includes getters and setters for Solidus classes as extension points.

Before extending any class, study the standard implementation of it carefully. Once you understand the implementation, you can use Solidus's provided extension points to subclass or re-implement it for your store.

Solidus's service class extension points can be found as part of the Spree::AppConfiguration object, where each line that begins with class_name_attribute defines a different extension point.

Example usage

When you extend a class, you can change the behavior of a single feature or your entire store.

For example, you can change what appears in a customer's search results by extending the Spree::Core::Search::Base. This way, you do not need to completely rewrite Solidus's searcher. Solidus provides a class extension point for this:

# /core/lib/spree/app_configuration.rb
class_name_attribute :searcher_class, default: 'Spree::Core::Search::Base'

Note that if you do not use this extension point, then searcher_class defaults to using Spree::Core::Search::Base.

Extending the searcher is a multi-step process:

1. Create a custom searcher for your store at /lib/mystore/product_search.rb.
2. Define a private get_base_scope method to override in classes that inherit from Spree::Core::Search::Base.
3. Connect your searcher to the :searcher_class extension point in the Solidus initializer at config/initializers/spree.rb.

In your MyStore::ProductSearch class, rewrite the Spree::Core::Search::Base's get_base_scope method with our desired functionality:

# /lib/mystore/product_search.rb
module MyStore
  class ProductSearch < Spree::Core::Search::Base

    private

    def get_base_scope
      super.where("name LIKE '%rails%'")
    end
  end
end

This searcher only displays search results that pass on to the base_scope variable and have the string rails in their name.

Then, you can apply your searcher to the extension point in your config/initializers/spree.rb initializer:

# /config/initializers/spree.rb
require 'my_store/product_search'

Spree.config do |config|
  config.searcher_class = MyStore::ProductSearch
end

Now, when search is built it uses your extended MyStore::ProductSearch functionality instead of the default functionality.

Generating extension points

If you see yourself overriding a class with a definable interface, and there is no associated extension point, consider submitting a pull request for your changeable class.