gistfile1.rb

require 'rubygems'
gem 'xml-mapping'
require 'xml/mapping'

class Foo
  include XML::Mapping
  def self.file_data
    @file_data ||= nil
  end
  def self.file_data=(value)
    @file_data = value
  end

  def initialize(file)
    if self.class.file_data.nil?
      puts "LOADING!!!"
      self.class.file_data = self.class.load_from_file(file)
    end
  end
end

Foo.new("/Users/atmos/.samurai/git/xc88/cluster.xml")
Foo.new("/Users/atmos/.samurai/git/xc88/cluster.xml")
Foo.new("/Users/atmos/.samurai/git/xc88/cluster.xml")

gistfile2.txt