StateMachines Active Record Integration

The Active Record 5.1+ integration adds support for database transactions, automatically saving the record, named scopes, validation errors.

Add this line to your application's Gemfile:

gem 'state_machines-activerecord'

And then execute:

$ bundle

Or install it yourself as:

$ gem install state_machines-activerecord

For the complete usage guide, see http://www.rubydoc.info/github/state-machines/state_machines-activerecord/StateMachines/Integrations/ActiveRecord

class Vehicle < ApplicationRecord
  state_machine :initial => :parked do
    before_transition :parked => any - :parked, :do => :put_on_seatbelt
    after_transition any => :parked do |vehicle, transition|
      vehicle.seatbelt = 'off'
    end
    around_transition :benchmark

    event :ignite do
      transition :parked => :idling
    end

    state :first_gear, :second_gear do
      validates :seatbelt_on, presence: true
    end
  end

  def put_on_seatbelt
    ...
  end

  def benchmark
    ...
    yield
    ...
  end
end

Usage of the generated scopes (assuming default column state):

Vehicle.with_state(:parked)                         # also plural #with_states
Vehicle.without_states(:first_gear, :second_gear)   # also singular #without_state

As mentioned in StateMachines::Machine#state, you can define behaviors, like validations, that only execute for certain states. One important caveat here is that, due to a constraint in ActiveRecord's validation framework, custom validators will not work as expected when defined to run in multiple states. For example:

class Vehicle < ApplicationRecord
  state_machine do
    state :first_gear, :second_gear do
      validate :speed_is_legal
    end
  end
end

In this case, the :speed_is_legal validation will only get run for the :second_gear state. To avoid this, you can define your custom validation like so:

class Vehicle < ApplicationRecord
  state_machine do
    state :first_gear, :second_gear do
      validate {|vehicle| vehicle.speed_is_legal}
    end
  end
end

1. Fork it ( https://github.com/state-machines/state_machines-activerecord/fork )
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request