module StateMachine::Integrations::MongoMapper

Adds support for integrating state machines with MongoMapper models.

Examples

Below is an example of a simple state machine defined within a MongoMapper model:

class Vehicle
  include MongoMapper::Document

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

The examples in the sections below will use the above class as a reference.

Actions

By default, the action that will be invoked when a state is transitioned is the save action. This will cause the record to save the changes made to the state machine’s attribute. Note that if any other changes were made to the record prior to transition, then those changes will be saved as well.

For example,

vehicle = Vehicle.create          # => #<Vehicle id: 1, name: nil, state: "parked">
vehicle.name = 'Ford Explorer'
vehicle.ignite                    # => true
vehicle.reload                    # => #<Vehicle id: 1, name: "Ford Explorer", state: "idling">

Events

As described in StateMachine::InstanceMethods#state_machine, event attributes are created for every machine that allow transitions to be performed automatically when the object’s action (in this case, :save) is called.

In MongoMapper, these automated events are run in the following order:

For example,

vehicle = Vehicle.create          # => #<Vehicle id: 1, name: nil, state: "parked">
vehicle.state_event               # => nil
vehicle.state_event = 'invalid'
vehicle.valid?                    # => false
vehicle.errors.full_messages      # => ["State event is invalid"]

vehicle.state_event = 'ignite'
vehicle.valid?                    # => true
vehicle.save                      # => true
vehicle.state                     # => "idling"
vehicle.state_event               # => nil

Note that this can also be done on a mass-assignment basis:

vehicle = Vehicle.create(:state_event => 'ignite')  # => #<Vehicle id: 1, name: nil, state: "idling">
vehicle.state                                       # => "idling"

This technique is always used for transitioning states when the save action (which is the default) is configured for the machine.

Security implications

Beware that public event attributes mean that events can be fired whenever mass-assignment is being used. If you want to prevent malicious users from tampering with events through URLs / forms, the attribute should be protected like so:

class Vehicle
  include MongoMapper::Document

  attr_protected :state_event
  # attr_accessible ... # Alternative technique

  state_machine do
    ...
  end
end

If you want to only have some events be able to fire via mass-assignment, you can build two state machines (one public and one protected) like so:

class Vehicle
  include MongoMapper::Document

  attr_protected :state_event # Prevent access to events in the first machine

  state_machine do
    # Define private events here
  end

  # Public machine targets the same state as the private machine
  state_machine :public_state, :attribute => :state do
    # Define public events here
  end
end

Validations

As mentioned in StateMachine::Machine#state, you can define behaviors, like validations, that only execute for certain states. One important caveat here is that, due to a constraint in MongoMapper’s validation framework, custom validators will not work as expected when defined to run in multiple states. For example:

class Vehicle
  include MongoMapper::Document

  state_machine do
    ...
    state :first_gear, :second_gear do
      validate :speed_is_legal
    end
  end
end

In this case, the :speed_is_legal validation will only get run for the :second_gear state. To avoid this, you can define your custom validation like so:

class Vehicle
  include MongoMapper::Document

  state_machine do
    ...
    state :first_gear, :second_gear do
      validate {|vehicle| vehicle.speed_is_legal}
    end
  end
end

Validation errors

If an event fails to successfully fire because there are no matching transitions for the current record, a validation error is added to the record’s state attribute to help in determining why it failed and for reporting via the UI.

For example,

vehicle = Vehicle.create(:state => 'idling')  # => #<Vehicle id: 1, name: nil, state: "idling">
vehicle.ignite                                # => false
vehicle.errors.full_messages                  # => ["State cannot transition via \"ignite\""]

If an event fails to fire because of a validation error on the record and not because a matching transition was not available, no error messages will be added to the state attribute.

In addition, if you’re using the ignite! version of the event, then the failure reason (such as the current validation errors) will be included in the exception that gets raised when the event fails. For example, assuming there’s a validation on a field called name on the class:

vehicle = Vehicle.new
vehicle.ignite!       # => StateMachine::InvalidTransition: Cannot transition state via :ignite from :parked (Reason(s): Name cannot be blank)

Scopes

To assist in filtering models with specific states, a series of basic scopes are defined on the model for finding records with or without a particular set of states.

These scopes are essentially the functional equivalent of the following definitions:

class Vehicle
  include MongoMapper::Document

  def self.with_states(*states)
    all(:conditions => {:state => {'$in' => states}})
  end
  # with_states also aliased to with_state

  def self.without_states(*states)
    all(:conditions => {:state => {'$nin' => states}})
  end
  # without_states also aliased to without_state
end

Note, however, that the states are converted to their stored values before being passed into the query.

Because of the way named scopes work in MongoMapper, they cannot be chained.

Note that states can also be referenced by the string version of their name:

Vehicle.with_state('parked')

Callbacks

All before/after transition callbacks defined for MongoMapper models behave in the same way that other MongoMapper callbacks behave. The object involved in the transition is passed in as an argument.

For example,

class Vehicle
  include MongoMapper::Document

  state_machine :initial => :parked do
    before_transition any => :idling do |vehicle|
      vehicle.put_on_seatbelt
    end

    before_transition do |vehicle, transition|
      # log message
    end

    event :ignite do
      transition :parked => :idling
    end
  end

  def put_on_seatbelt
    ...
  end
end

Note, also, that the transition can be accessed by simply defining additional arguments in the callback block.

Callback Order

Callbacks occur in the following order. Callbacks specific to state_machine are bolded. The remaining callbacks are part of MongoMapper.

Internationalization

Any error message that is generated from performing invalid transitions can be localized. The following default translations are used:

en:
  mongo_mapper:
    errors:
      messages:
        invalid: "is invalid"
        # %{value} = attribute value, %{state} = Human state name
        invalid_event: "cannot transition when %{state}"
        # %{value} = attribute value, %{event} = Human event name, %{state} = Human current state name
        invalid_transition: "cannot transition via %{event}"

You can override these for a specific model like so:

en:
  mongo_mapper:
    errors:
      models:
        user:
          invalid: "is not valid"

In addition to the above, you can also provide translations for the various states / events in each state machine. Using the Vehicle example, state translations will be looked for using the following keys, where model_name = “vehicle”, machine_name = “state” and state_name = “parked”:

Event translations will be looked for using the following keys, where model_name = “vehicle”, machine_name = “state” and event_name = “ignite”:

An example translation configuration might look like so:

es:
  mongo_mapper:
    state_machines:
      states:
        parked: 'estacionado'
      events:
        park: 'estacionarse'

Public Class Methods

active?() click to toggle source
  # File lib/state_machine/integrations/mongo_mapper/versions.rb
5 def self.active?
6   !defined?(::MongoMapper::Plugins)
7 end
matching_ancestors() click to toggle source

Classes that include MongoMapper::Document will automatically use the MongoMapper integration.

    # File lib/state_machine/integrations/mongo_mapper.rb
312 def self.matching_ancestors
313   %w(MongoMapper::Document)
314 end

Public Instance Methods

callback_terminator() click to toggle source
   # File lib/state_machine/integrations/mongo_mapper/versions.rb
63 def callback_terminator
64 end
filter_attributes(object, attributes) click to toggle source
   # File lib/state_machine/integrations/mongo_mapper/versions.rb
 9 def filter_attributes(object, attributes)
10   attributes
11 end
invalidate(object, attribute, message, values = []) click to toggle source
   # File lib/state_machine/integrations/mongo_mapper/versions.rb
38 def invalidate(object, attribute, message, values = [])
39   object.errors.add(self.attribute(attribute), generate_message(message, values))
40 end
load_locale() click to toggle source
   # File lib/state_machine/integrations/mongo_mapper/versions.rb
52 def load_locale
53 end
supports_observers?() click to toggle source
   # File lib/state_machine/integrations/mongo_mapper/versions.rb
55 def supports_observers?
56   false
57 end
supports_validations?() click to toggle source
   # File lib/state_machine/integrations/mongo_mapper/versions.rb
59 def supports_validations?
60   true
61 end
translate(klass, key, value) click to toggle source
   # File lib/state_machine/integrations/mongo_mapper/versions.rb
66 def translate(klass, key, value)
67   value.to_s.humanize.downcase
68 end

Protected Instance Methods

around_save(object) { || ... } click to toggle source

Runs state events around the machine’s :save action

    # File lib/state_machine/integrations/mongo_mapper.rb
367 def around_save(object)
368   object.class.state_machines.transitions(object, action).perform { yield }
369 end
attribute_key() click to toggle source

Gets the Mongoid key for this machine’s attribute (if it exists)

    # File lib/state_machine/integrations/mongo_mapper.rb
328 def attribute_key
329   owner_class.keys[attribute.to_s]
330 end
create_with_scope(name) click to toggle source

Creates a scope for finding records with a particular state or states for the attribute

    # File lib/state_machine/integrations/mongo_mapper.rb
373 def create_with_scope(name)
374   define_scope(name, lambda {|values| {:conditions => {attribute => {'$in' => values}}}})
375 end
create_without_scope(name) click to toggle source

Creates a scope for finding records without a particular state or states for the attribute

    # File lib/state_machine/integrations/mongo_mapper.rb
379 def create_without_scope(name)
380   define_scope(name, lambda {|values| {:conditions => {attribute => {'$nin' => values}}}})
381 end
define_action_hook() click to toggle source

Uses around callbacks to run state events if using the :save hook

Calls superclass method
    # File lib/state_machine/integrations/mongo_mapper.rb
350         def define_action_hook
351           if action_hook == :save
352             define_helper :instance, <<-end_eval, __FILE__, __LINE__ + 1
353               def save(*)
354                 self.class.state_machine(#{name.inspect}).send(:around_save, self) { super }
355               end
356               
357               def save!(*)
358                 self.class.state_machine(#{name.inspect}).send(:around_save, self) { super } || raise(::MongoMapper::DocumentNotValid.new(self))
359               end
360             end_eval
361           else
362             super
363           end
364         end
define_scope(name, scope) click to toggle source

Defines a new scope with the given name

    # File lib/state_machine/integrations/mongo_mapper.rb
384 def define_scope(name, scope)
385   lambda {|model, values| model.query.merge(model.query(scope.call(values)))}
386 end
define_state_accessor() click to toggle source

Skips defining reader/writer methods since this is done automatically

    # File lib/state_machine/integrations/mongo_mapper.rb
344 def define_state_accessor
345   owner_class.key(attribute, String) unless attribute_key
346   super
347 end
define_state_initializer() click to toggle source

Defines an initialization hook into the owner class for setting the initial state of the machine before any attributes are set on the object

    # File lib/state_machine/integrations/mongo_mapper.rb
335         def define_state_initializer
336           define_helper :instance, <<-end_eval, __FILE__, __LINE__ + 1
337             def initialize(*args)
338               self.class.state_machines.initialize_states(self, :static => :force) { super }
339             end
340           end_eval
341         end
owner_class_attribute_default() click to toggle source

Gets the db default for the machine’s attribute

    # File lib/state_machine/integrations/mongo_mapper.rb
323 def owner_class_attribute_default
324   attribute_key && attribute_key.default_value
325 end
runs_validations_on_action?() click to toggle source

Only runs validations on the action if using :save

    # File lib/state_machine/integrations/mongo_mapper.rb
318 def runs_validations_on_action?
319   action == :save
320 end