Mongoid::CounterCache

counter_cache.rb

module Mongoid
  module CounterCache
    extend ActiveSupport::Concern

    included do
    end

    module ClassMethods
      def counter_cache(name, counter_field = nil)
        counter_field ||= "#{self.name.underscore.pluralize}_counter"

        # -- field --
        reflection = self.reflect_on_association(name)
        reflection.klass.field counter_field, type: Integer, default: 0

        # -- callbacks --
        after_create "increment_#{counter_field}"
        after_destroy "decrement_#{counter_field}"

        # -- method definitions --
        define_method "increment_#{counter_field}" do
          relation = send(name)
          relation.inc(counter_field, 1)
        end

        define_method "decrement_#{counter_field}" do
          relation = send(name)
          relation.inc(counter_field, -1)
        end

        define_method "recount_#{counter_field}" do
          relation = send(name)
          relation.set(counter_field, self.where(relation.foreign_key => relation._id).count)
        end
      end
    end
  end
end