Ruby NullObject

class NullObject
  def nil?; true; end
  def !; true end
  def to_a; []; end
  def to_s(*args); ""; end
  def to_str(*args); ""; end
  def to_f(*args); 0.0; end
  def to_i(*args); 0; end
  def method_missing(*args, &blk)
    self
  end
end