state_machine_callback_with_keyword_argument.rb

# sample task model
#
# > rails c
# irb(main):004:0> t.finish
# "-------> notify_done with 0"
# "-------> notify_done with 1"
# "-------> notify_done with 2"
# "-------> notify_done end"
# => true
class Task < ActiveRecord::Base
  state_machine initial: :todo do
    state :todo
    state :doing
    state :done

    event :start do
      transition from: :todo, to: :doing
    end

    event :finish do
      transition from: :doing, to: :done
    end

    event :redo do
      transition from: :done, to: :todo
    end

    after_transition to: :todo, do: :notify_todo
    after_transition to: :doing, do: :notify_doing
    after_transition to: :done do |task, transition|
      task.notify_done
    end
  end

  def notify_todo
    p "-------> #{__method__}"
  end

  def notify_doing
    p "-------> #{__method__}"
  end

  def notify_done(cnt: 0)
    p "-------> #{__method__} with #{cnt}"
    raise
  rescue => e
    sleep Math.exp(cnt)
    cnt += 1
    retry if cnt < 3
  ensure
    p "-------> #{__method__} end"
  end
end