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:
-
before validation - Run before callbacks and persist new states, then validate
-
before save - If validation was skipped, run before callbacks and persist new states, then save
-
after save - Run after callbacks
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.
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”:
-
mongo_mapper.state_machines.#{model_name}.#{machine_name}.states.#{state_name}
-
mongo_mapper.state_machines.#{model_name}.states.#{state_name}
-
mongo_mapper.state_machines.#{machine_name}.states.#{state_name}
-
mongo_mapper.state_machines.states.#{state_name}
Event
translations will be looked for using the following keys, where model_name
= “vehicle”, machine_name
= “state” and event_name
= “ignite”:
-
mongo_mapper.state_machines.#{model_name}.#{machine_name}.events.#{event_name}
-
mongo_mapper.state_machines.#{model_name}.events.#{event_name}
-
mongo_mapper.state_machines.#{machine_name}.events.#{event_name}
-
mongo_mapper.state_machines.events.#{event_name}
An example translation configuration might look like so:
es: mongo_mapper: state_machines: states: parked: 'estacionado' events: park: 'estacionarse'
Public Class Methods
# File lib/state_machine/integrations/mongo_mapper/versions.rb 5 def self.active? 6 !defined?(::MongoMapper::Plugins) 7 end
Whether this integration is available. Only true if MongoMapper::Document is defined.
# File lib/state_machine/integrations/mongo_mapper.rb 296 def self.available? 297 defined?(::MongoMapper::Document) 298 end
Should this integration be used for state machines in the given class? Classes that include MongoMapper::Document will automatically use the MongoMapper
integration.
# File lib/state_machine/integrations/mongo_mapper.rb 303 def self.matches?(klass) 304 klass <= ::MongoMapper::Document 305 end
Public Instance Methods
# File lib/state_machine/integrations/mongo_mapper/versions.rb 52 def action_hook 53 action == :save ? :create_or_update : super 54 end
# File lib/state_machine/integrations/mongo_mapper/versions.rb 67 def callback_terminator 68 end
# File lib/state_machine/integrations/mongo_mapper/versions.rb 9 def filter_attributes(object, attributes) 10 attributes 11 end
# 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
# File lib/state_machine/integrations/mongo_mapper/versions.rb 56 def load_locale 57 end
# File lib/state_machine/integrations/mongo_mapper/versions.rb 59 def supports_observers? 60 false 61 end
# File lib/state_machine/integrations/mongo_mapper/versions.rb 63 def supports_validations? 64 true 65 end
# File lib/state_machine/integrations/mongo_mapper/versions.rb 70 def translate(klass, key, value) 71 value.to_s.humanize.downcase 72 end
Protected Instance Methods
Runs state events around the machine's :save action
# File lib/state_machine/integrations/mongo_mapper.rb 340 def around_save(object) 341 object.class.state_machines.transitions(object, action).perform { yield } 342 end
Creates a scope for finding records with a particular state or states for the attribute
# File lib/state_machine/integrations/mongo_mapper.rb 346 def create_with_scope(name) 347 define_scope(name, lambda {|values| {:conditions => {attribute => {'$in' => values}}}}) 348 end
Creates a scope for finding records without a particular state or states for the attribute
# File lib/state_machine/integrations/mongo_mapper.rb 352 def create_without_scope(name) 353 define_scope(name, lambda {|values| {:conditions => {attribute => {'$nin' => values}}}}) 354 end
Uses around callbacks to run state events if using the :save hook
# File lib/state_machine/integrations/mongo_mapper.rb 331 def define_action_hook 332 if action_hook == :save 333 owner_class.set_callback(:save, :around, self, :prepend => true) 334 else 335 super 336 end 337 end
Defines a new scope with the given name
# File lib/state_machine/integrations/mongo_mapper.rb 357 def define_scope(name, scope) 358 lambda {|model, values| model.query.merge(model.query(scope.call(values)))} 359 end
Skips defining reader/writer methods since this is done automatically
StateMachine::Integrations::ActiveModel#define_state_accessor
# File lib/state_machine/integrations/mongo_mapper.rb 325 def define_state_accessor 326 owner_class.key(attribute, String) unless owner_class.keys.include?(attribute.to_s) 327 super 328 end
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 316 def define_state_initializer 317 define_helper :instance, <<-end_eval, __FILE__, __LINE__ + 1 318 def initialize(*args) 319 self.class.state_machines.initialize_states(self) { super } 320 end 321 end_eval 322 end
Only runs validations on the action if using :save
# File lib/state_machine/integrations/mongo_mapper.rb 309 def runs_validations_on_action? 310 action == :save 311 end