transition

Transactions

Every transition is wrapped within a transaction to ensure changes during transition callbacks can be rolled back in case of failure.

For example:

  class Message < ActiveRecord::Base
  end

  Vehicle.state_machine do
    before_transition do |vehicle, transition|
      Message.create(:content => transition.inspect)
      false
    end
  end

  vehicle = Vehicle.create      # => #<Vehicle id: 1, name: nil, state: "parked">
  vehicle.ignite                # => false
  Message.count                 # => 0

• Typical transaction roll back:
  • A before_ callback(s) halts the callback chain
  • Attempts to save the record failed
• If an after_ callback halts the chain, the previous result still applies and the transaction is not rolled back
• To turn off transactions:

  class Vehicle < ActiveRecord::Base
    state_machine :initial => :parked, :use_transactions => false do
      ...
    end
  end