Heteromorphic Fantasy: Obie's state_machine (2012)

A walk-through of state machines with @obie's gem.

Code examples here: https://github.com/damncabbage/state_machine_example

Transcript

1. Heteromorphic Fantasy @obrie’s state_machine
3. machine? state What is a
4. :caterpillar
5. :pupa
7. Caterpillar
8. Caterpillar Pupa
9. Caterpillar Pupa Eldritch Horror
10. Caterpillar Pupa Pupate Eldritch Horror Emerge
11. Let’s find a tamer example.
12. Vending Machine
13. state_machine
14. :idle :awaiting selection push_button insert_dollar
15. state :idle # Free: v.state == :idle v.idle?
16. event :push_button # Free: v.can_push_button?
17. :idle :awaiting selection push_button insert_dollar
18. :idle :awaiting selection push_button insert_dollar :accepting money insert_dollar insert_dollar insert_dollar
19. :idle :awaiting selection push_button insert_dollar :accepting money insert_dollar insert_dollar insert_dollar crowbar :broken
20. Extra Goodies
21. Per-State class_eval
22. state :details do validates :name, :presence => true validates :email, :presence => true end state :shipping do validates :address, :presence => true end
23. state :on do def volume dial_rotation * 100 / max_rotation end end state :mute do def volume 0 end end
24. Multiple State Machines
25. state_machine :state do state :idle state :awaiting_selection end state_machine :coin_slot do state :open state :closed end
26. State Values
27. state_machine :alarm do state :on, :value => 1 state :off, :value => 0 end
28. Real World Where can I find some Examples already?
29. Spree Commerce http://github.com/spree/spree
30. state_machine :initial => 'cart', :use_transactions => false do event :next do transition :from => 'cart', :to => 'address' transition :from => 'address', :to => 'delivery' transition :from => 'delivery', :to => 'payment', :if => :payment_required? transition :from => 'delivery', :to => 'complete' transition :from => 'confirm', :to => 'complete' transition :from => 'payment', :to => 'confirm', :if => Proc.new { |order| order.payment_method && order.payment_method.payment_profiles_supported? } transition :from => 'payment', :to => 'complete' end event :cancel { transition :to => 'canceled', :if => :allow_cancel? } event :return { transition :to => 'returned', :from => 'awaiting_return' } event :resume { transition :to => 'resumed', :from => 'canceled', :if => :allow_resume? } event :authorize_return { transition :to => 'awaiting_return' } before_transition :to => 'complete' { |order| order.process_payments! } before_transition :to => ['delivery'] do |order| order.shipments.each { |s| s.destroy unless s.shipping_method.available_to_order?(order) } end after_transition :to => 'complete', :do => :finalize! after_transition :to => 'delivery', :do => :create_tax_charge! after_transition :to => 'payment', :do => :create_shipment! after_transition :to => 'resumed', :do => :after_resume after_transition :to => 'canceled', :do => :after_cancel end
31. @damncabbage http://robhoward.id.au obrie/state_machine damncabbage/state_machine_example GitHub