custom_getters.rb

class Post < ActiveRecord::Base
 
  has_many :authors

  attr_accessor :post_authors_cache

  def post_authors
    process_post_authors if post_authors_cache.nil?
    post_authors_cache
  end

  private

  def process_post_authors
    #do some crazy stuff here and set the post_authors_cache
    self.post_authors_cache = {} #some crazy hash of stuff based on some inane business logic
  end

end