http://blog.darkhax.com/2009/09/14/get-your-wordpress-out-of-my-blogging-software

cache.rb

class Cache < ActiveRecord::Base
  serialize :value
  
  def self.get(key, max_age = 1.hour)
    item = Cache.first(:conditions => { :key => key })
    if block_given?
      if item.nil? || item.updated_at < max_age.ago
        begin
          value = yield
          Cache.put(key,value)
          value
        rescue Exception => e
          p e.message
          item.nil? ? nil : item.value
        end
      else
        item.value
      end
    else
      item.nil? ? nil : item.value
    end
  end
  
  def self.put(key,value)
    c = Cache.find_or_create_by_key(key)
    c.value = value
    c.save
    c.touch
  end
  
  def self.purge(key)
    items = key.nil? ? Cache.all : Cache.all(:conditions => { :key => key })
    items.each do |item|
      item.destroy
    end
  end
end