Class Specialisations (Composition + Dependency injection) by Sandi Metz

gistfile1.rb

# Class Specialisations  (Composition + Dependency injection)

class House
  DATA = [1,2,3,4,5,6]
  attr_reader :data

  def initialize(orderer: DefaultOrderer.new, formatter: DefaultFormatter.new)
    # @data = formatter.format(orderer.order(DATA))
    formatted_data = formatter.format(DATA)
    @data = orderer.order(formatted_data)
  end
end


class DefaultOrderer
  def order(data)
    data
  end
end

class DefaultFormatter
  def format(data)
    data
  end
end


class RandomOrderer
  def order(data)
    data.shuffle
  end
end

class EchoFormatter
  def format(data)
    data.zip(data).flatten
  end
end


h = House.new
puts "h: #{h.data}"


h_rand = House.new(orderer: RandomOrderer.new)
puts "h_rand: #{h_rand.data}"

h_echo = House.new(formatter: EchoFormatter.new)
puts "h_echo: #{h_echo.data}"

h_rand_echo = House.new(orderer: RandomOrderer.new, formatter: EchoFormatter.new)
puts "h_rand_echo: #{h_rand_echo.data}"

#RESULT:
# razor@razor-VM:~/RUBY/dependencies$ ruby house.rb 
# h: [1, 2, 3, 4, 5, 6]
# h_rand: [6, 3, 5, 2, 1, 4]
# h_echo: [1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6]
# h_rand_echo: [2, 1, 5, 3, 6, 2, 4, 3, 4, 6, 5, 1]