The document discusses state machines and provides examples of state machines for different scenarios like a vending machine, alarm system, and e-commerce site. It explains some key concepts like states, events, transitions between states, and using state machines to model real-world systems. It also provides extra details on per-state validations, multiple state machines, and assigning state values.

1. Heteromorphic
Fantasy
@obrie’s state_machine

4. Booze.

5. What is a
state
machine?

6. :caterpillar

7. :pupa

9. Caterpillar

10. Caterpillar Pupa

11. Eldritch
Caterpillar Pupa
Horror

12. Eldritch
Caterpillar Pupa
Pupate Emerge Horror

13. Let’s find a
tamer

14. Vending

15. state_machine

16. insert_dollar
:awaiting
:idle
selection
push_button

17. state :idle
# Free:
v.state == :idle

18. event :push_button
# Free:
v.can_push_button?

19. insert_dollar
:awaiting
:idle
selection
push_button

20. push_button
:awaiting
:idle
insert_dollar selection
insert_dollar insert_dollar
:accepting
money
insert_dollar

21. :broken
crowbar
push_button
:awaiting
:idle
insert_doll selection
insert_dollar insert_dollar
:accepting
money
insert_dollar

22. Extra Goodies

23. Per-State
class_eval

24. state :details do
validates :name, :presence => true
validates :email, :presence => true
end
state :shipping do
validates :address, :presence => true
end

25. state :on do
def volume
dial_rotation * 100 / max_rotation
end
end
state :mute do
def volume
0
end
end

26. Multiple State
Machines

27. state_machine :state do
state :idle
state :awaiting_selection
end
state_machine :coin_slot do
state :open
state :closed
end

28. State Values

29. state_machine :alarm do
state :on, :value => 1
state :off, :value => 0
end

30. Can we have some
Real World
Examples already?

31. Spree
http://github.com/spree/

32. GitHub
obrie/state_machine
@damncabbage
http://robhoward.id.au