Naming is hard

item_caching.rb

module ItemCaching
  extend ActiveSupport::Concern

  def self.cache_all_items_grouped_by_group
    Rails.cache.fetch(:items_grouped_by_group) do
      Item.all.group_by {|i| i.group_id }
    end
  end


  def self.belonging_to_group_from_cache(group_id)
    Rails.cache.read(:items_grouped_by_group)[group_id] || []
  end
end

COMMENT IS FOR 1b897ab384
This is a concern that gets mixed into Item. So a call would be

Item.belonging_to_group_from_cache(group.id)

Completely unsatisfied with the method names. The mentioned method returns multiple items but doesn't indicate that by its name for example.

Item.cached_for_group(group.id) is a good suggestion.

cached_for_group it is.

Made the model concern more general.