Module: Stately::Core

Defined in:
lib/stately.rb

Instance Method Summary collapse

Instance Method Details

#stately(*opts, &block) ⇒ Object

Define a new Stately state machine.

As an example, let’s say you have an Order object and you’d like an elegant state machine for it. Here’s one way you might set it up:

Class Order do
  stately start: :processing do
    state :completed do
      prevent_from :refunded

      before_transition from: :processing, do: :calculate_total
      after_transition do: :email_receipt

      validate :validates_credit_card
    end

    state :invalid do
      prevent_from :completed, :refunded
    end

    state :refunded do
      allow_from :completed

      after_transition do: :email_receipt
    end
  end
end

This example is doing quite a few things, paraphrased as:

* It sets up a new state machine using the default state attribute on Order to store the
  current state. It also indicates the initial state should be :processing.
* It defines three states: :completed, :refunded, and :invalid
* Order can transition to the completed state from all but the refunded state. Similar
  definitions are setup for the other two states.
* Callbacks are setup using before_transition and after_transition
* Validations are added. If a validation fails, it prevents the transition.

Stately tries hard not to surprise you. In a typical Stately implementation, you’ll always have an after_transition, primarily to call save (or whatever the equivalent is to store the instance’s current state).



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# File 'lib/stately.rb', line 52

def stately(*opts, &block)
  options = opts.last.is_a?(Hash) ? opts.last : {}
  options[:attr] ||= :state

  self.stately_machine = Stately::Machine.new(options[:attr], options[:start])
  self.stately_machine.instance_eval(&block) if block_given?

  include Stately::InstanceMethods
end

#stately_machine ⇒ Object

Get the current Stately::Machine object



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# File 'lib/stately.rb', line 63

def stately_machine
  @@stately_machine
end

#stately_machine=(obj) ⇒ Object

Set the current Stately::Machine object



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# File 'lib/stately.rb', line 68

def stately_machine=(obj)
  @@stately_machine = obj
end