class Object
  # Takes a hash and creates (singleton) attr_writers for each key.
  #
  #   require 'facet/object/with_accessor'
  #
  #   with_writer { :x => 1, :y => 2 }
  #   @x           #=> 1
  #   @y           #=> 2
  #   self.x = 3
  #   self.y = 4
  #   @x           #=> 3
  #   @y           #=> 4
  #
  def with_writer(h)
    (class << self ; self ; end).send( :attr_writer, *h.keys )
    h.each { |k,v| instance_variable_set("@#{k}", v) }
  end
end