How to properly extend String and abstract in new functionality using the Proxy Pattern without overriding native Ruby primitives.

Proxy Pattern in Ruby

#!/usr/bin/env ruby
#
# How to properly extend String and abstract in new functionality using the Proxy Pattern
# without overriding native Ruby primitives.
#
# [og](http://www.fngtps.com/2006/09/the-proxy-pattern-in-ruby)
#

require 'rubygems' 
require 'bacon'

module Formatting

  class Formatter < String
    alias :to_str :to_s

    def initialize(str)
      super
      @str = str
    end

    def to_str
      @str
    end

    def format(str=nil)
      Formatter.new(str || self)
    end
  end

  def self.register(mod)
    Formatter.send :include, mod
  end

end

module UpTheCase
  def upthecase
    format @str.upcase!
  end
end

module UnNewLine
  def unnewlined
    format @str.gsub!(/\r\n/, '')
  end
end

describe Formatting::Formatter do

  before do
    @string = Formatting::Formatter.new("test out  \r\n")
  end

  it "should register UpTheCase's instance methods" do
    Formatting.register UpTheCase
    Formatting::Formatter.instance_methods.should.include(*UpTheCase.instance_methods)
  end

  it "should register UnNewLine's instance methods" do
    Formatting.register UnNewLine
    Formatting::Formatter.instance_methods.should.include(*UnNewLine.instance_methods)
  end
  
  it "should up the case" do
    Formatting.register UpTheCase
    @string.format.upthecase.should == "TEST OUT  \r\n"
  end

  it "should remove new lines" do
    Formatting.register UnNewLine
    @string.format.unnewlined.should == "test out  "
  end
  
end

Bacon.summary_on_exit