introduce state vo

ecommerce/ordering/lib/ordering/order.rb

@@ -9,13 +9,13 @@ class Order
 
     def initialize(id)
       @id = id
-      @state = :draft
+      @state = State.draft
       @basket = Basket.new
     end
 
     def submit(order_number)
-      raise OrderHasExpired if @state.equal?(:expired)
-      raise AlreadySubmitted unless @state.equal?(:draft)
+      raise OrderHasExpired if @state.expired?
+      raise AlreadySubmitted unless @state.draft?
       apply OrderSubmitted.new(
         data: {
           order_id: @id,
@@ -26,7 +26,7 @@ def submit(order_number)
     end
 
     def accept
-      raise InvalidState unless @state.equal?(:submitted)
+      raise InvalidState unless @state.submitted?
       apply OrderPlaced.new(
         data: {
           order_id: @id,
@@ -37,7 +37,7 @@ def accept
     end
 
     def reject
-      raise InvalidState unless @state.equal?(:submitted)
+      raise InvalidState unless @state.submitted?
       apply OrderRejected.new(
         data: {
           order_id: @id
@@ -46,12 +46,12 @@ def reject
     end
 
     def expire
-      raise AlreadySubmitted unless @state.equal?(:draft)
+      raise AlreadySubmitted unless @state.draft?
       apply OrderExpired.new(data: { order_id: @id })
     end
 
     def add_item(product_id)
-      raise AlreadySubmitted unless @state.equal?(:draft)
+      raise AlreadySubmitted unless @state.draft?
       apply ItemAddedToBasket.new(
         data: {
           order_id: @id,
@@ -61,16 +61,16 @@ def add_item(product_id)
     end
 
     def remove_item(product_id)
-      raise AlreadySubmitted unless @state.equal?(:draft)
+      raise AlreadySubmitted unless @state.draft?
       apply ItemRemovedFromBasket.new(data: { order_id: @id, product_id: product_id })
     end
 
     on OrderPlaced do |event|
-      @state = :accepted
+      @state = State.new(:accepted)
     end
 
     on OrderExpired do |event|
-      @state = :expired
+      @state = State.expired
     end
 
     on ItemAddedToBasket do |event|
@@ -83,11 +83,11 @@ def remove_item(product_id)
 
     on OrderSubmitted do |event|
       @order_number = event.data[:order_number]
-      @state = :submitted
+      @state = State.submitted
     end
 
     on OrderRejected do |event|
-      @state = :draft
+      @state = State.draft
     end
 
     class Basket
@@ -112,5 +112,35 @@ def quantity(product_id)
         order_lines[product_id]
       end
     end
+
+    class State
+      def self.draft
+        new(:draft)
+      end
+
+      def self.submitted
+        new(:submitted)
+      end
+
+      def self.expired
+        new(:expired)
+      end
+
+      def initialize(state)
+        @state = state
+      end
+
+      def draft?
+        @state.equal?(:draft)
+      end
+
+      def submitted?
+        @state.equal?(:submitted)
+      end
+
+      def expired?
+        @state.equal?(:expired)
+      end
+    end
   end
 end