An early version of a Rails settings model

gistfile1.rb

class Setting < ActiveRecord::Base
  @@settings = {}

  belongs_to :record, :polymorphic => true

  validates_uniqueness_of :key
  
  before_save :expire_cache

  # Retrieve and cache a value for a key
  def self.retrieve_value(key)
    record = find_by_key(key) if @@settings[key].nil?
    @@settings[key] ||= record.value if record.present?
    @@settings[key]
  end
  
  # Expire settings cache
  def self.expire_cache
    @@settings = {}
  end
  
  def expire_cache
    self.class.expire_cache
  end
  
  def self.cache
    @@settings
  end
  
  # Obtain the value from a key. If no record exists, return
  # nil.
  def self.find_by_key(key)
    self.where(:key => key).first
  end
  
  private
    # Yikes, this is getting unruley
    def self.method_missing(method_id, *arguments, &block)
      # Setup a counter to avoid annoying recursion
      @mm_counter ||= 0
      @mm_counter += 1

      if @mm_counter > 1
        @mm_counter = 0
        super
      else
        value = retrieve_value(method_id)
        if value.nil?
          @mm_counter = 0
          super
        else
          @mm_counter = 0
          value
        end
      end
    end
end