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
   

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3. machine?
   state
   What is a
   

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4. :caterpillar
   

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5. :pupa
   

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7. Caterpillar
   

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8. Caterpillar Pupa
   

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9. Caterpillar Pupa
   Eldritch
   Horror
   

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10. Caterpillar Pupa
    Pupate
    Eldritch
    Horror
    Emerge
    

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11. Let’s find a
    tamer
    example.
    

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12. Vending Machine
    

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13. state_machine
    

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14. :idle
    :awaiting
    selection
    push_button
    insert_dollar
    

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15. state :idle
    # Free:
    v.state == :idle
    v.idle?
    

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

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17. :idle
    :awaiting
    selection
    push_button
    insert_dollar
    

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

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19. :idle
    :awaiting
    selection
    push_button
    insert_dollar
    :accepting
    money
    insert_dollar
    insert_dollar
    insert_dollar
    crowbar
    :broken
    

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20. Extra Goodies
    

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21. Per-State
    class_eval
    

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

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

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24. Multiple State
    Machines
    

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

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26. State Values
    

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

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28. Real World
    Where can I find some
    Examples
    already?
    

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29. Spree Commerce
    http://github.com/spree/spree
    

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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
    

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

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