list_models.rb

# frozen_string_literal: true

require 'sequel'

module QontrolDB
  module SequelPlugins
    # This Sequel Plugin stores all models that are created throughout the app, to make a list of
    # them available to anyone who needs it.
    #
    # It works by creating a hook called whenever a class is created by inheriting from the
    # `Sequel::Model` class (meaning a new Model is created in the application). This new class is
    # thus remembered as a Business Domain Model.
    #
    # It is for example useful to freeze model classes as explained here:
    #   https://sequel.jeremyevans.net/rdoc/files/doc/code_order_rdoc.html#label-Finalize+Associations+and+Freeze+Model+Classes+and+Database
    #
    class ListModels
      class << self
        # @return [Array<Sequel::Model>] All models classes created throughout the app at call time
        attr_reader :models

        # Register a new class model that has been created
        #
        # @param [Class] model_klass
        def register_new_model(model_klass)
          @models ||= []
          @models << model_klass
        end
      end

      module ClassMethods
        # Calls when a model inherits from Sequel::Model with this plugin enabled, i.e. when a new
        # Model class is created.
        #
        # So we take this opportunity to remember the class in the ListModels list.
        #
        # @param [Class] model
        def inherited(model)
          ListModels.register_new_model(model)

          super
        end
      end
    end
  end
end