state / event

Symbol Vs. String Definition

• In all examples you'll notice states and events are referenced as symbols as that's the best practice. However, you can also use numbers or strings:

  class Vehicle
  state_machine :initial => 'parked' do
    event 'ignite' do
      transition 'parked' => 'idling'
    end
    ...
  end
  end
  

• Type used for referencing states and events in the machine definition must be consistent or you'll encounter this error:

class Vehicle
  state_machine do
    event :ignite do
      transition :parked => 'idling'
    end
  end
end

# => ArgumentError: "idling" state defined as String, :parked defined as Symbol; all states must be consistent

• Consistency is only required within the definition. e.g. if a machine's helper methods are called with input from external sources, such as a web form, StateMachine will still map that input to a String or Symbol:

class Vehicle
  state_machine :initial => :parked do
    event :ignite do
      transition :parked => :idling
    end
  end
end

v = Vehicle.new     # => #<Vehicle:0xb71da5f8 @state="parked">
v.state?('parked')  # => true
v.state?(:parked)   # => true