Head First Design Patterns - Decorator - Starbuzz

starbuzz_coffee.rb

require 'attr_extras'

module StarbuzzCoffee
  class Beverage
    attr_reader :description

    def initialize
      @description = "Unknown Beverage"
    end

    def cost
      raise NotImplementedError
    end
  end

  class CondimentDecorator < Beverage
    def description
      raise NotImplementedError
    end
  end

  class Espresso < Beverage
    def initialize
      @description = 'Espresso'
    end

    def cost
      1.99
    end
  end

  class HouseBlend < Beverage
    def initialize
      @description = 'House Blend Coffee'
    end

    def cost
      0.89
    end
  end

  class DarkRoast < Beverage
    def initialize
      @description = 'Dark Roast Coffee'
    end

    def cost
      0.99
    end
  end

  class Mocha < CondimentDecorator
    pattr_initialize :beverage

    def description
      "#{beverage.description}, Mocha"
    end

    def cost
      beverage.cost + 0.20
    end
  end

  class Soy < CondimentDecorator
    pattr_initialize :beverage

    def description
      "#{beverage.description}, Soy"
    end

    def cost
      beverage.cost + 0.15
    end
  end

  class Whip < CondimentDecorator
    pattr_initialize :beverage

    def description
      "#{beverage.description}, Whip"
    end

    def cost
      beverage.cost + 0.10
    end
  end

  def self.main
    beverages = []

    beverages[0] = Espresso.new

    beverages[1] = DarkRoast.new
    beverages[1] = Mocha.new(beverages[1])
    beverages[1] = Mocha.new(beverages[1])
    beverages[1] = Whip.new(beverages[1])

    beverages[2] = HouseBlend.new
    beverages[2] = Soy.new(beverages[2])
    beverages[2] = Mocha.new(beverages[2])
    beverages[2] = Whip.new(beverages[2])

    beverages.each do |beverage|
      puts "#{beverage.description} $#{beverage.cost}"
    end
  end
end

StarbuzzCoffee.main