Ruby DSL Blocks

starbucks.rb

    module Starbucks

      def self.order(&block)
        order = Order.new
        order.instance_eval(&block)
        return order.drinks
      end

      class Order

        attr_reader :drinks

        def initialize
          @drinks = []
        end

        def short
          @size = "small"
          return self
        end

        def tall
          @size = "medium"
          return self
        end

        def grande
          @size = "large"
          return self
        end

        def venti
          @size = "extra large"
          return self
        end

        def coffee
          @drink = "coffee"
          build_drink
        end

        def decaf
          @drink = "decaffeinated coffee"
          build_drink
        end

        def half_caff
          @drink = "regular and decaffeinated coffee mixed together"
          build_drink
        end

        def americano
          @drink = "espresso"
          build_drink
        end

        def mocha
          @drink = "espresso mixed with chocolate, milk, and topped with whipped cream"
          build_drink
        end

        def cappuchino
          @drink = "espresso mixed with milk and topped with steamed milk"
          build_drink
        end

        def no_whip
          @adjective = "without the whipped cream"
          return self
        end

        def non_fat
          @adjective = "with non-fat milk"
          return self
        end

        def breve
          @adjective = "with half and half"
          return self
        end

        def extra_shot
          @adjective = "with an extra shot of espresso"
          return self
        end

        def soy
          @adjective = "with soy milk"
          return self
        end

        def extra_hot
          @adjective = "with super heated milk"
          return self
        end
        private

        def build_drink
          drink = "#{@size} cup of #{@drink}"
          drink << " #{@adjective}" if @adjective
          @drinks << drink

          @size = @drink = @adjective = nil
        end
      end

    end

    require File.expand_path(File.dirname(__FILE__) + "/starbucks")

    #### Specs ####

    describe "Starbucks" do

      it "should handle empty orders" do
        Starbucks.order {}.should eql([])
      end

      it "should handle regular coffee with all the sizes" do
        Starbucks.order do
          short.coffee
          tall.coffee
          grande.coffee
          venti.coffee
        end.should eql(["small cup of coffee",
                        "medium cup of coffee",
                        "large cup of coffee",
                        "extra large cup of coffee"])
      end
      it "should deal with types of drinks" do
        Starbucks.order do
          short.decaf
          short.half_caff
          short.americano
          short.mocha
          short.cappuchino
        end.should eql(["small cup of decaffeinated coffee",
                        "small cup of regular and decaffeinated coffee mixed together",
                        "small cup of espresso",
                        "small cup of espresso mixed with chocolate, milk, and topped with whipped cream",
                        "small cup of espresso mixed with milk and topped with steamed milk"])
      end

      it "should handle the adjectives" do
        Starbucks.order do
          short.no_whip.coffee
          short.non_fat.coffee
          short.breve.coffee
          short.extra_shot.coffee
          short.soy.coffee
          short.extra_hot.coffee
        end.should eql(["small cup of coffee without the whipped cream",
                        "small cup of coffee with non-fat milk",
                        "small cup of coffee with half and half",
                        "small cup of coffee with an extra shot of espresso",
                        "small cup of coffee with soy milk",
                        "small cup of coffee with super heated milk",])
      end

    end