sample builder script in Ruby

builder.rb

module Builder
  def self.method_missing name, *args, &block
    tag = Tag.new
    tag.send(name, *args, &block).flatten.join
  end 

  class Tag 
    def initialize
      @tags = []
    end 
  
    def method_missing *args, &block
      name = args.shift
      if block
        child = Tag.new
        child.instance_eval(&block)
        block_value = tagify(name, child.valuate)
        @tags << block_value
        block_value
      else
        value = args.shift
        @tags << {:name => name, :value => value}
      end 
    end 

    def valuate
      @tags.map do |tag|
        tag.kind_of?(Hash) ?
          tagify(tag[:name], tag[:value]) :
          tag
      end
    end

    def tagify name, value
      ["<#{name}>", value, "</#{name}>"]
    end
  end
end

require 'expectations'        
Sample = <<TREE.gsub(/\s/, '')
<root>
  <book>
    <title>souseki1</title>
    <author>souseki</author>
  </book>
  <book>
    <title>souseki2</title>
    <author>souseki</author>
  </book>
  <book>
    <title>souseki3</title>
    <author>souseki</author>
  </book>
</root>
TREE    

Expectations do
  expect Sample do
    titles = %w[ souseki1 souseki2 souseki3 ]
    Builder.root do
      titles.each do |t|
        book do
          title t
          author "souseki"
        end
      end
    end
  end
end