gistfile1.rb

module DefaultOrder
  module_function
  def order(data)
    data
  end
end

module RandomOrder
  module_function
  def order(data)
    data.shuffle
  end
end

module DefaultFormatter
  module_function
  def format(parts)
    parts
  end
end

module EchoFormatter
  module_function
  def format(parts)
    parts.zip(parts).flatten
  end
end

class House
  DATA =[
    "the cat that killed",
    "the rat that ate",
    "the malt that lay in",
    "the house that Jack built"
  ]

  def initialize
    @data = orderer.order(DATA)
  end

  def recite
    (1..@data.length).map {|i| line(i)}.join("\n")
  end

  def line(number)
    "This is #{phrase(number)}.\n"
  end

  def phrase(number)
    parts(number).join(" ")
  end

  def parts(number)
    formatter.format(@data.last(number))
  end

  def orderer
    DefaultOrder
  end

  def formatter
    DefaultFormatter
  end
end

class RandomHouse < House
  def orderer
    RandomOrder
  end
end

class EchoHouse < House
  def formatter
    EchoFormatter
  end
end

class RandomEchoHouse < House
  def orderer
    RandomOrder
  end
  def formatter
    EchoFormatter
  end
end


puts House.new.recite
puts "="*88
puts "="*88
puts "="*88
puts RandomHouse.new.recite
puts "="*88
puts "="*88
puts "="*88
puts EchoHouse.new.recite
puts "="*88
puts "="*88
puts "="*88
puts RandomEchoHouse.new.recite

See https://www.youtube.com/watch?v=OMPfEXIlTVE for context.