not_found.rb

# http://gist.github.com/301471
#
# Not Found - (C) 2010 [email protected] - MIT License
#
# Quick hack to have a string that always says "not found",
# even when multiple methods are chained to it.
# 
#
# E.g.: 
#
# >> x = NotFound.new
# => "not found"
# >> x.oai_dc.authors.antani
# => "oai_dc authors antani not found"
# >> x.something(:that).will(:have, :attributes)
# => "something that will have attributes not found"
#
#
# Want to filter some methods? Here we go:
#
# >> x = NotFound.new(:_no => [:join])
# => "not found"
# >> x.prot.antani.join("\n").pizello
# => "document prot antani pizello not found"
#
#
# And one more thing: NotFound is blank!
#
# >> x.blank?
# => true
# >> x.nil?
# => true
#
# Efficiency? Quite efficient:
#
# >> bench(10000) { NotFound.new('document', :_no => [:join, :prot]).prot.antani.join("\n").pizello }
# 10000 iterations: 1.205242 (0.000121 per iteration)
#
# (bench() is here: http://gist.github.com/301485)
# 
# Have fun :-)
#

class NotFound < String
  def initialize(*attr)
    @filters = attr.pop[:_no] \
      if attr.last.kind_of?(Hash) &&
        attr.last.has_key?(:_no)

    @attr = attr.flatten

    replace((@attr + ['not found']).join(' '))
  end
 
  undef_method :[], :type, :id
  def blank?; true end
  alias :nil? :blank?
 
  def method_missing(meth, *args)
    forward =
      if @filters && @filters.include?(meth)
        @attr
      else
        [@attr, meth, args]
      end

    self.class.new(forward, :_no => @filters)
  end
end