Adds support for integrating state machines with MongoMapper models.
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.
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">
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.
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
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.
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.
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.
# File lib/state_machine/integrations/mongo_mapper/versions.rb, line 5 def self.active? !defined?(::MongoMapper::Plugins) end
Whether this integration is available. Only true if MongoMapper::Document is defined.
# File lib/state_machine/integrations/mongo_mapper.rb, line 199 def self.available? defined?(::MongoMapper::Document) 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, line 206 def self.matches?(klass) klass <= ::MongoMapper::Document end
# File lib/state_machine/integrations/mongo_mapper/versions.rb, line 52 def action_hook action == :save ? :create_or_update : super end
# File lib/state_machine/integrations/mongo_mapper/versions.rb, line 71 def callback_terminator end
# File lib/state_machine/integrations/mongo_mapper/versions.rb, line 9 def filter_attributes(object, attributes) attributes end
# File lib/state_machine/integrations/mongo_mapper/versions.rb, line 38 def invalidate(object, attribute, message, values = []) object.errors.add(self.attribute(attribute), generate_message(message, values)) end
# File lib/state_machine/integrations/mongo_mapper/versions.rb, line 56 def load_locale end
# File lib/state_machine/integrations/mongo_mapper/versions.rb, line 67 def supports_dirty_tracking?(object) true end
# File lib/state_machine/integrations/mongo_mapper/versions.rb, line 59 def supports_observers? false end
Runs state events around the machine's :save action
# File lib/state_machine/integrations/mongo_mapper.rb, line 243 def around_save(object) object.class.state_machines.transitions(object, action).perform { yield } end
Creates a scope for finding records with a particular state or states for the attribute
# File lib/state_machine/integrations/mongo_mapper.rb, line 249 def create_with_scope(name) define_scope(name, lambda {|values| {:conditions => {attribute => {'$in' => values}}}}) end
Creates a scope for finding records without a particular state or states for the attribute
# File lib/state_machine/integrations/mongo_mapper.rb, line 255 def create_without_scope(name) define_scope(name, lambda {|values| {:conditions => {attribute => {'$nin' => values}}}}) end
Uses around callbacks to run state events if using the :save hook
# File lib/state_machine/integrations/mongo_mapper.rb, line 234 def define_action_hook if action_hook == :save owner_class.set_callback(:save, :around, self, :prepend => true) else super end end
Defines a new scope with the given name
# File lib/state_machine/integrations/mongo_mapper.rb, line 260 def define_scope(name, scope) lambda {|model, values| model.query.merge(model.query(scope.call(values)))} end
Skips defining reader/writer methods since this is done automatically
# File lib/state_machine/integrations/mongo_mapper.rb, line 228 def define_state_accessor owner_class.key(attribute, String) unless owner_class.keys.include?(attribute) super 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, line 219 def define_state_initializer define_helper :instance, def initialize(*args) self.class.state_machines.initialize_states(self) { super } end, __FILE__, __LINE__ + 1 end
ActiveModel's use of method_missing / respond_to for attribute methods breaks both ancestor lookups and defined?(super). Need to special-case the existence of query attribute methods.
# File lib/state_machine/integrations/mongo_mapper.rb, line 267 def owner_class_ancestor_has_method?(method) method == "#{name}?" || super end
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