rbarraud · July 24, 2014 07:16 · Jul 23, 2014 · Jul 23, 2014 · Jul 23, 2014 · Jul 23, 2014
diff --git a/01_turnstile.rb b/01_turnstile.rb
@@ -1,7 +1,6 @@
 # Our simple example of a Turnstile state machine.
 
 class Turnstile
-
   def initialize
     @state = "Locked"
   end

diff --git a/03_shopping_cart_state.rb b/03_shopping_cart_state.rb
@@ -1,3 +1,5 @@
+# This is the final version of our ShoppingCartState code as presented.
+
 module ShoppingCartState
   StateError = Class.new(RuntimeError)
 

diff --git a/04_shopping_cart_state_spec.rb b/04_shopping_cart_state_spec.rb
@@ -1,21 +1,5 @@
 require './03_shopping_cart_state'
-
-# This is code I pulled in from another project to mock the
-# `update_attributes!` method.  Sorry about the noise.
-module MockUpdateAttributes
-  def mock_update_attributes_on(model)
-    update_proc = proc do |attrs|
-      attrs.each do |attr,value|
-        setter = "#{attr}=".to_sym
-        expect(model).to respond_to attr
-        expect(model).to respond_to setter
-        model.public_send setter, value
-      end
-    end
-    allow(model).to receive(:update_attributes!, &update_proc)
-    model
-  end
-end
+require './09_mock_update_attributes'
 
 describe ShoppingCartState do
   include MockUpdateAttributes

diff --git a/05_shopping_cart.rb b/05_shopping_cart.rb
@@ -1,8 +1,8 @@
-# This is a fake AR base class.
-
 require './03_shopping_cart_state'
 require './99_ar'
 
+# The final version of our ShoppingCart class, as described in the talk.
+
 class ShoppingCart < AR::Base
 
   has_many :line_items

diff --git a/09_shopping_cart.rb b/09_shopping_cart.rb
@@ -3,6 +3,8 @@
 require './99_ar'
 
 # This is the ShoppingCart using the StateDelegator mixin.
+# As mentioned in the improvements section of the talk.
+
 class ShoppingCart < AR::Base
   include StateDelegator
 

diff --git a/10_shopping_cart_spec.rb b/10_shopping_cart_spec.rb
@@ -1,5 +1,8 @@
 require './09_shopping_cart.rb'
 
+# Exactly the same specs as in `06_shopping_cart_spec.rb` except we're testing
+# the StateDelegator version of the ShoppingCart.
+
 describe ShoppingCart do
   %w| line_items add_item! cancel! pay! ship! fulfil! state state= |.each do |method|
     it { should respond_to method }

diff --git a/98_mock_update_attributes.rb b/98_mock_update_attributes.rb
@@ -0,0 +1,16 @@
+# This is code I pulled in from another project to mock the
+# `update_attributes!` method.  Sorry about the noise.
+module MockUpdateAttributes
+  def mock_update_attributes_on(model)
+    update_proc = proc do |attrs|
+      attrs.each do |attr,value|
+        setter = "#{attr}=".to_sym
+        expect(model).to respond_to attr
+        expect(model).to respond_to setter
+        model.public_send setter, value
+      end
+    end
+    allow(model).to receive(:update_attributes!, &update_proc)
+    model
+  end
+end
diff --git a/99_ar.rb b/99_ar.rb
@@ -1,4 +1,4 @@
-# This is a fake AR base class for our purposes..
+# This is a fake AR base class sufficient for our purposes.
 module AR
 
   class Base

diff --git a/05_shopping_cart.rb b/05_shopping_cart.rb
@@ -1,25 +1,7 @@
 # This is a fake AR base class.
 
 require './03_shopping_cart_state'
-
-module AR
-  class Base
-    attr_accessor :state, :line_items
-
-    def initialize
-      @state = 'New'
-      @line_items = []
-    end
-
-    def update_attributes! attrs={}
-      attrs.each do |attr, value|
-        public_send "#{attr}=", value
-      end
-    end
-
-    def self.has_many _; end
-  end
-end
+require './99_ar'
 
 class ShoppingCart < AR::Base
 
@@ -52,7 +34,4 @@ def send_successful_shipping_email
   def current_state
     ShoppingCartState.const_get(state).new(self)
   end
-
-
-
 end
diff --git a/07_state_delegator.rb b/07_state_delegator.rb
@@ -0,0 +1,31 @@
+# Mix this module into your model to automatically create delegates
+# to the relevant state class.
+# This module assumes that if you are mixing it into the `Order` class
+# then it will be delegating to the `OrderState` class heirarchy.
+
+module StateDelegator
+
+  def self.included model_class
+    model_name = model_class.to_s
+    state_name = "#{model_name}State"
+    state_base = const_get "#{state_name}::Base"
+
+    state_methods = state_base.public_instance_methods(false)
+
+    mixin = Module.new do
+      state_methods.each do |state_method|
+        define_method state_method do |*args|
+          current_state.public_send(state_method, *args)
+        end
+      end
+
+      define_method :current_state do
+        Object.const_get("::#{state_name}").const_get(state).new(self)
+      end
+
+      private :current_state
+    end
+    model_class.send :include, mixin
+  end
+
+end
diff --git a/08_state_delegator_spec.rb b/08_state_delegator_spec.rb
@@ -0,0 +1,48 @@
+require './07_state_delegator'
+
+describe StateDelegator do
+  before do
+    class DemoState
+      class Base
+        def initialize stateful; end
+        def foo?; false; end
+        def bar?; false; end
+      end
+    end
+
+    class Demo < Struct.new(:state)
+      include StateDelegator
+    end
+  end
+
+  after do
+    DemoState.send :remove_const, :Base
+    Object.send :remove_const, :DemoState
+    Object.send :remove_const, :Demo
+  end
+
+  subject { Demo.new 'Base' }
+
+  describe 'delegator definition' do
+    %w| foo? bar? |.each do |predicate|
+      describe "##{predicate}" do
+        it { should respond_to predicate }
+
+        it 'delegates to the state instance' do
+          expect_any_instance_of(DemoState::Base).to receive(predicate)
+          subject.public_send predicate
+        end
+      end
+    end
+  end
+
+  describe 'state finder method' do
+    it 'has the current_state method' do
+      expect(subject.private_methods).to include(:current_state)
+    end
+
+    it 'delegates to the state class' do
+      expect(subject.send :current_state).to be_a(DemoState::Base)
+    end
+  end
+end
diff --git a/09_shopping_cart.rb b/09_shopping_cart.rb
@@ -0,0 +1,28 @@
+require './03_shopping_cart_state'
+require './07_state_delegator'
+require './99_ar'
+
+# This is the ShoppingCart using the StateDelegator mixin.
+class ShoppingCart < AR::Base
+  include StateDelegator
+
+  has_many :line_items
+
+  def ship!
+    current_state.ship! do
+      get_tracking_ticket_no
+    end
+
+    send_successful_shipping_email
+  end
+
+  private
+
+  def get_tracking_ticket_no
+    # noop
+  end
+
+  def send_successful_shipping_email
+    # noop
+  end
+end
diff --git a/10_shopping_cart_spec.rb b/10_shopping_cart_spec.rb
@@ -0,0 +1,38 @@
+require './09_shopping_cart.rb'
+
+describe ShoppingCart do
+  %w| line_items add_item! cancel! pay! ship! fulfil! state state= |.each do |method|
+    it { should respond_to method }
+  end
+
+  describe 'State delegation' do
+    %w| add_item! cancel! pay! ship! fulfil! |.each do |action|
+      let(:current_state) { double :current_state }
+      before do
+        allow(subject).to receive(:current_state).and_return(current_state)
+      end
+
+      describe "##{action}" do
+        it 'delegates to current state' do
+          expect(current_state).to receive(action)
+          subject.public_send(action)
+        end
+      end
+    end
+  end
+
+  describe '#ship!' do
+    before { subject.state = 'ReadyToShip' }
+
+    it 'retrieves tracking info' do
+      expect(subject).to receive(:get_tracking_ticket_no)
+      subject.ship!
+    end
+
+    it 'sends a shipping email' do
+      expect(subject).to receive(:send_successful_shipping_email)
+      subject.ship!
+    end
+  end
+
+end
diff --git a/99_ar.rb b/99_ar.rb
@@ -0,0 +1,20 @@
+# This is a fake AR base class for our purposes..
+module AR
+
+  class Base
+    attr_accessor :state, :line_items
+
+    def initialize
+      @state = 'New'
+      @line_items = []
+    end
+
+    def update_attributes! attrs={}
+      attrs.each do |attr, value|
+        public_send "#{attr}=", value
+      end
+    end
+
+    def self.has_many _; end
+  end
+end
diff --git a/03_shopping_cart_state.rb b/03_shopping_cart_state.rb
@@ -47,6 +47,7 @@ def fulfil!
 
   class ReadyToShip < Cancellable
     def ship!
+      yield if block_given?
       @cart.update_attributes! state: 'Shipped'
     end
   end

diff --git a/05_shopping_cart.rb b/05_shopping_cart.rb
@@ -0,0 +1,58 @@
+# This is a fake AR base class.
+
+require './03_shopping_cart_state'
+
+module AR
+  class Base
+    attr_accessor :state, :line_items
+
+    def initialize
+      @state = 'New'
+      @line_items = []
+    end
+
+    def update_attributes! attrs={}
+      attrs.each do |attr, value|
+        public_send "#{attr}=", value
+      end
+    end
+
+    def self.has_many _; end
+  end
+end
+
+class ShoppingCart < AR::Base
+
+  has_many :line_items
+
+  %w| add_item! cancel! pay! fulfil! |.each do |action|
+    define_method action do |*args|
+      current_state.public_send action, *args
+    end
+  end
+
+  def ship!
+    current_state.ship! do
+      get_tracking_ticket_no
+    end
+
+    send_successful_shipping_email
+  end
+
+  private
+
+  def get_tracking_ticket_no
+    # noop
+  end
+
+  def send_successful_shipping_email
+    # noop
+  end
+
+  def current_state
+    ShoppingCartState.const_get(state).new(self)
+  end
+
+
+
+end
diff --git a/06_shopping_cart_spec.rb b/06_shopping_cart_spec.rb
@@ -0,0 +1,38 @@
+require './05_shopping_cart.rb'
+
+describe ShoppingCart do
+  %w| line_items add_item! cancel! pay! ship! fulfil! state state= |.each do |method|
+    it { should respond_to method }
+  end
+
+  describe 'State delegation' do
+    %w| add_item! cancel! pay! ship! fulfil! |.each do |action|
+      let(:current_state) { double :current_state }
+      before do
+        allow(subject).to receive(:current_state).and_return(current_state)
+      end
+
+      describe "##{action}" do
+        it 'delegates to current state' do
+          expect(current_state).to receive(action)
+          subject.public_send(action)
+        end
+      end
+    end
+  end
+
+  describe '#ship!' do
+    before { subject.state = 'ReadyToShip' }
+
+    it 'retrieves tracking info' do
+      expect(subject).to receive(:get_tracking_ticket_no)
+      subject.ship!
+    end
+
+    it 'sends a shipping email' do
+      expect(subject).to receive(:send_successful_shipping_email)
+      subject.ship!
+    end
+  end
+
+end
diff --git a/03_shopping_cart_state.rb b/03_shopping_cart_state.rb
@@ -0,0 +1,59 @@
+module ShoppingCartState
+  StateError = Class.new(RuntimeError)
+
+  class Base
+    def initialize cart
+      @cart = cart
+    end
+
+    %w| add_item! pay! cancel! ship! fulfil! |.each do |action|
+      define_method action do |*_|
+        raise StateError, "Can't call #{action} from #{@cart.state}"
+      end
+    end
+  end
+
+  class Cancellable < Base
+    def cancel!
+      @cart.update_attributes! state: 'Cancelled'
+    end
+  end
+
+  class New < Cancellable
+    def add_item! item
+      @cart.line_items << item
+    end
+
+    def pay!
+      @cart.update_attributes! state: 'Paid'
+    end
+  end
+
+  class Paid < Cancellable
+    def fulfil!
+      if @cart.all_in_stock?
+        @cart.update_attributes! state: 'ReadyToShip'
+      else
+        @cart.update_attributes! state: 'Backorder'
+      end
+    end
+  end
+
+  class Backorder < Cancellable
+    def fulfil!
+      @cart.update_attributes! state: 'ReadyToShip'
+    end
+  end
+
+  class ReadyToShip < Cancellable
+    def ship!
+      @cart.update_attributes! state: 'Shipped'
+    end
+  end
+
+  class Cancelled < Base
+  end
+
+  class Shipped < Base
+  end
+end
diff --git a/04_shopping_cart_state_spec.rb b/04_shopping_cart_state_spec.rb
@@ -0,0 +1,114 @@
+require './03_shopping_cart_state'
+
+# This is code I pulled in from another project to mock the
+# `update_attributes!` method.  Sorry about the noise.
+module MockUpdateAttributes
+  def mock_update_attributes_on(model)
+    update_proc = proc do |attrs|
+      attrs.each do |attr,value|
+        setter = "#{attr}=".to_sym
+        expect(model).to respond_to attr
+        expect(model).to respond_to setter
+        model.public_send setter, value
+      end
+    end
+    allow(model).to receive(:update_attributes!, &update_proc)
+    model
+  end
+end
+
+describe ShoppingCartState do
+  include MockUpdateAttributes
+
+  let(:cart) { mock_update_attributes_on Struct.new(:state).new }
+  subject { described_class.new cart }
+
+  describe ShoppingCartState::Base do
+
+    %w| add_item! pay! cancel! ship! fulfil! |.each do |action|
+      describe "##{action}" do
+        it 'raises a StateError' do
+          expect { subject.public_send action }.to raise_error ShoppingCartState::StateError
+        end
+      end
+    end
+
+  end
+
+  describe ShoppingCartState::Cancellable do
+    it { should be_a ShoppingCartState::Base }
+
+    describe '#cancel!' do
+      it 'changes the cart state to Cancelled' do
+        expect { subject.cancel! }.to change { cart.state }.to('Cancelled')
+      end
+    end
+  end
+
+  describe ShoppingCartState::New do
+    it { should be_a ShoppingCartState::Cancellable }
+
+    describe '#add_item!' do
+      it 'adds an item to the cart' do
+        allow(cart).to receive(:line_items).and_return([])
+        expect { subject.add_item! :item }.to change { cart.line_items.length }.by(1)
+      end
+    end
+
+    describe '#pay!' do
+      it 'changes the cart state to Paid' do
+        expect { subject.pay! }.to change { cart.state }.to('Paid')
+      end
+    end
+  end
+
+  describe ShoppingCartState::Paid do
+    it { should be_a ShoppingCartState::Cancellable }
+
+    describe '#fulfil!' do
+      context "When all line items are in stock" do
+        it 'changes the cart state to ReadyToShip' do
+          allow(cart).to receive(:all_in_stock?).and_return(true)
+          expect { subject.fulfil! }.to change { cart.state }.to('ReadyToShip')
+        end
+      end
+
+      context "When all line items are not in stock" do
+        it 'changes the cart state to Backorder' do
+          allow(cart).to receive(:all_in_stock?).and_return(false)
+          expect { subject.fulfil! }.to change { cart.state }.to('Backorder')
+        end
+      end
+    end
+  end
+
+  describe ShoppingCartState::Backorder do
+    it { should be_a ShoppingCartState::Cancellable }
+
+    describe '#fulfil!' do
+      it 'changes the cart state to ReadyToShip' do
+        expect { subject.fulfil! }.to change { cart.state }.to('ReadyToShip')
+      end
+    end
+  end
+
+  describe ShoppingCartState::ReadyToShip do
+    it { should be_a ShoppingCartState::Cancellable }
+
+    describe '#ship!' do
+      it 'changes the cart state to Shipped' do
+        expect { subject.ship! }.to change { cart.state }.to('Shipped')
+      end
+    end
+  end
+
+  describe ShoppingCartState::Cancelled do
+    it { should be_a ShoppingCartState::Base }
+    it { should_not be_a ShoppingCartState::Cancellable }
+  end
+
+  describe ShoppingCartState::Shipped do
+    it { should be_a ShoppingCartState::Base }
+    it { should_not be_a ShoppingCartState::Cancellable }
+  end
+end
diff --git a/01_turnstile.rb b/01_turnstile.rb
@@ -0,0 +1,24 @@
+# Our simple example of a Turnstile state machine.
+
+class Turnstile
+
+  def initialize
+    @state = "Locked"
+  end
+
+  def push!
+    @state = "Locked" if unlocked?
+  end
+
+  def pay!
+    @state = "Unlocked" if locked?
+  end
+
+  def locked?
+    @state == "Locked"
+  end
+
+  def unlocked?
+    @state = "Unlocked"
+  end
+end
diff --git a/02_turnstile_spec.rb b/02_turnstile_spec.rb
@@ -0,0 +1,32 @@
+require './01_turnstile'
+
+describe Turnstile do
+  subject { described_class.new }
+  it { should be_locked }
+
+  context "When it is locked" do
+    context "And we push it" do
+      before { subject.push! }
+      it { should be_locked }
+    end
+
+    context "And we pay it" do
+      before { subject.pay! }
+      it { should be_unlocked }
+    end
+  end
+
+  context "When it is unlocked" do
+    before { subject.pay! }
+
+    context "And we push it" do
+      before { subject.push! }
+      it { should be_locked }
+    end
+
+    context "And we pay it" do
+      before { subject.pay! }
+      it { should be_unlocked }
+    end
+  end
+end
diff --git a/foo.rb b/foo.rb
@@ -1 +0,0 @@
-sdfsd

diff --git a/foo.rb b/foo.rb
@@ -0,0 +1 @@
+sdfsd
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