gistfile1.rb

module NameIdCache
  def self.included(base)
    m = Module.new
    
    base.all.each do |record|
      cache_key = NameIdCache.cache_key(base, record)
      Rails.cache.write(cache_key, record.id)
      
      m.__send__(:define_method, record.name) do
        Rails.cache.fetch(cache_key) do
          base.find_by_name!(record.name).id
        end
      end
    end

    base.extend(m)
  end

  def self.cache_key(base, record)
    [self.name, base.name, record.name].join(":")
  end
end

class DeliveryState < ActiveRecord::Base
  include NameIdCache
end

# This results in:
# DeliveryState Load (0.2ms)  SELECT `delivery_states`.* FROM `delivery_states` 
# => DeliveryState(id: integer, name: string, created_at: datetime, updated_at: datetime) 

DeliveryState.all.inspect # => [#<DeliveryState id: 1, name: "queued", created_at: "2012-03-06 12:10:35", updated_at: "2012-03-06 12:10:35">]


#
# How does it work?
#

# This does not hit the DB
DeliveryState.queued # => 1
NameIdCache.cache_key(DeliveryState, DeliveryState.first) # => "NameIdCache:DeliveryState:queued"
Rails.cache.read("NameIdCache:DeliveryState:queued") # => 1

#
# What if I nuke the cache?
#

Rails.cache.delete("NameIdCache:DeliveryState:queued") # => true 
Rails.cache.read("NameIdCache:DeliveryState:queued") # => nil 

# Results in DeliveryState Load (0.3ms)  SELECT `delivery_states`.* FROM `delivery_states` WHERE `delivery_states`.`name` = 'queued' LIMIT 1
DeliveryState.queued # => 1