Rails cacheable has_one

cacheable_has_one.rb

module CacheableHasOne
  extend ActiveSupport::Concern

  included do
    @build_cached_getter = ::Kernel.lambda do |cache_key, association_symbol|
      alias_method "_#{association_symbol}".to_sym, association_symbol

      define_method(association_symbol) do
        return send("_#{association_symbol}") unless persisted?

        if association(association_symbol).loaded?
          return instance_variable_get("@cached_#{association_symbol}") || send("_#{association_symbol}")
        end

        cached_value = Rails.cache.fetch cache_key do
          send("_#{association_symbol}")
        end
        cached_value.run_callbacks :initialize
        cached_value.class.set_callback :save, :after, -> { Rails.cache.delete cache_key }

        instance_variable_set("@cached_#{association_symbol}", cached_value)
        association(association_symbol).loaded!
        instance_variable_get("@cached_#{association_symbol}")
      end
    end

    @build_cached_setter = ::Kernel.lambda do |cache_key, association_symbol|
      alias_method "_#{association_symbol}=".to_sym, "#{association_symbol}=".to_sym

      define_method "#{association_symbol}=" do |value|
        Rails.cache.delete cache_key
        instance_variable_set("@cached_#{association_symbol}", nil)
        super(value)
      end
    end

    def self.cacheable_has_one(association_symbol, options)
      send(:has_one, association_symbol, options)
      instance_variable_set("@cached_#{association_symbol}", nil)
      cache_key = [self.class.name, to_param, association_symbol]

      @build_cached_getter.call(cache_key, association_symbol)
      @build_cached_setter.call(cache_key, association_symbol)
    end
  end
end