Add simple support for ActiveModel's StateMachine for ActiveRecord

5 files changed, 101 insertions, 0 deletions

diff --git a/activerecord/lib/active_record.rb b/activerecord/lib/active_record.rb
index 5e9ce0600a..68b0251982 100644
--- a/activerecord/lib/active_record.rb
+++ b/activerecord/lib/active_record.rb
@@ -65,6 +65,7 @@ module ActiveRecord
   autoload :SchemaDumper, 'active_record/schema_dumper'
   autoload :Serialization, 'active_record/serialization'
   autoload :SessionStore, 'active_record/session_store'
+  autoload :StateMachine, 'active_record/state_machine'
   autoload :TestCase, 'active_record/test_case'
   autoload :Timestamp, 'active_record/timestamp'
   autoload :Transactions, 'active_record/transactions'
diff --git a/activerecord/lib/active_record/state_machine.rb b/activerecord/lib/active_record/state_machine.rb
new file mode 100644
index 0000000000..aebd03344a
--- /dev/null
+++ b/activerecord/lib/active_record/state_machine.rb
@@ -0,0 +1,24 @@
+module ActiveRecord
+  module StateMachine #:nodoc:
+    extend ActiveSupport::Concern
+    include ActiveModel::StateMachine
+
+    included do
+      before_validation :set_initial_state
+      validates_presence_of :state
+    end
+
+    protected
+      def write_state(state_machine, state)
+        update_attributes! :state => state.to_s
+      end
+
+      def read_state(state_machine)
+        self.state.to_sym
+      end
+
+      def set_initial_state
+        self.state ||= self.class.state_machine.initial_state.to_s
+      end
+  end
+end
diff --git a/activerecord/test/cases/state_machine_test.rb b/activerecord/test/cases/state_machine_test.rb
new file mode 100644
index 0000000000..5d13668bab
--- /dev/null
+++ b/activerecord/test/cases/state_machine_test.rb
@@ -0,0 +1,42 @@
+require 'cases/helper'
+require 'models/traffic_light'
+
+class StateMachineTest < ActiveRecord::TestCase
+  def setup
+    @light = TrafficLight.create!
+  end
+
+  test "states initial state" do
+    assert @light.off?
+    assert_equal :off, @light.current_state
+  end
+
+  test "transition to a valid state" do
+    @light.reset
+    assert @light.red?
+    assert_equal :red, @light.current_state
+
+    @light.green_on
+    assert @light.green?
+    assert_equal :green, @light.current_state
+  end
+
+  test "transition does not persist state" do
+    @light.reset
+    assert_equal :red, @light.current_state
+    @light.reload
+    assert_equal "off", @light.state
+  end
+
+  test "transition does persists state" do
+    @light.reset!
+    assert_equal :red, @light.current_state
+    @light.reload
+    assert_equal "red", @light.state
+  end
+
+  test "transition to an invalid state" do
+    assert_raise(ActiveModel::StateMachine::InvalidTransition) { @light.yellow_on }
+    assert_equal :off, @light.current_state
+  end
+end
diff --git a/activerecord/test/models/traffic_light.rb b/activerecord/test/models/traffic_light.rb
new file mode 100644
index 0000000000..f8cfddbef9
--- /dev/null
+++ b/activerecord/test/models/traffic_light.rb
@@ -0,0 +1,27 @@
+class TrafficLight < ActiveRecord::Base
+  include ActiveRecord::StateMachine
+
+  state_machine do
+    state :off
+
+    state :red
+    state :green
+    state :yellow
+
+    event :red_on do
+      transitions :to => :red, :from => [:yellow]
+    end
+
+    event :green_on do
+      transitions :to => :green, :from => [:red]
+    end
+
+    event :yellow_on do
+      transitions :to => :yellow, :from => [:green]
+    end
+
+    event :reset do
+      transitions :to => :red, :from => [:off]
+    end
+  end
+end
diff --git a/activerecord/test/schema/schema.rb b/activerecord/test/schema/schema.rb
index 2b7d3856b7..1e47cdbaf6 100644
--- a/activerecord/test/schema/schema.rb
+++ b/activerecord/test/schema/schema.rb
@@ -448,6 +448,13 @@ ActiveRecord::Schema.define do
     t.integer :pet_id, :integer
   end
 
+  create_table :traffic_lights, :force => true do |t|
+    t.string   :location
+    t.string   :state
+    t.datetime :created_at
+    t.datetime :updated_at
+  end
+
   create_table :treasures, :force => true do |t|
     t.column :name, :string
     t.column :looter_id, :integer