Module | StateMachine::Integrations::DataMapper |
In: |
lib/state_machine/integrations/data_mapper/observer.rb
lib/state_machine/integrations/data_mapper/versions.rb lib/state_machine/integrations/data_mapper.rb |
Adds support for integrating state machines with DataMapper resources.
Below is an example of a simple state machine defined within a DataMapper resource:
class Vehicle include DataMapper::Resource property :id, Serial property :name, String property :state, String 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 resource to save the changes made to the state machine‘s attribute. Note that if any other changes were made to the resource 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 DataMapper, 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 # => #<DataMapper::Validate::ValidationErrors:0xb7a48b54 @errors={"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 DataMapper::Resource ... state_machine do ... end protected :state_event 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 DataMapper::Resource ... state_machine do # Define private events here end protected :state_event= # Prevent access to events in the first machine # Allow both machines to share the same state state_machine :public_state, :attribute => :state do # Define public events here end end
By default, the use of transactions during an event transition is turned off to be consistent with DataMapper. This means that if changes are made to the database during a before callback, but the transition fails to complete, those changes will not be rolled back.
For example,
class Message include DataMapper::Resource property :id, Serial property :content, String end Vehicle.state_machine do before_transition do |transition| Message.create(:content => transition.inspect) throw :halt end end vehicle = Vehicle.create # => #<Vehicle id=1 name=nil state="parked"> vehicle.ignite # => false Message.all.count # => 1
To turn on transactions:
class Vehicle include DataMapper::Resource ... state_machine :initial => :parked, :use_transactions => true do ... end end
If using the save action for the machine, this option will be ignored as the transaction behavior will depend on the save implementation within DataMapper. To avoid this, use a different action like so:
class Vehicle include DataMapper::Resource ... state_machine :initial => :parked, :use_transactions => false, :action => :save_state do ... end alias_method :save_state, :save 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 # => ["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)
To assist in filtering models with specific states, a series of class methods are defined on the model for finding records with or without a particular set of states.
These named scopes are the functional equivalent of the following definitions:
class Vehicle include DataMapper::Resource property :id, Serial property :state, String class << self def with_states(*states) all(:state => states.flatten) end alias_method :with_state, :with_states def without_states(*states) all(:state.not => states.flatten) end alias_method :without_state, :without_states end end
Note, however, that the states are converted to their stored values before being passed into the query.
Because of the way scopes work in DataMapper, they can be chained like so:
Vehicle.with_state(:parked).all(:order => [:id.desc])
Note that states can also be referenced by the string version of their name:
Vehicle.with_state('parked')
All before/after transition callbacks defined for DataMapper resources behave in the same way that other DataMapper hooks behave. Rather than passing in the record as an argument to the callback, the callback is instead bound to the object and evaluated within its context.
For example,
class Vehicle include DataMapper::Resource property :id, Serial property :state, String state_machine :initial => :parked do before_transition any => :idling do put_on_seatbelt end before_transition do |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.
In addition to support for DataMapper-like hooks, there is additional support for DataMapper observers. See StateMachine::Integrations::DataMapper::Observer for more information.
after_failure callbacks allow you to execute behaviors when a transition is allowed, but fails to save. This could be useful for something like auditing transition attempts. Since callbacks run within transactions in DataMapper, a save failure will cause any records that get created in your callback to roll back. Note that this is only a problem if the machine is configured to use transactions. If it is, you can work around this issue like so:
DataMapper.setup(:default, 'mysql://localhost/app') DataMapper.setup(:logs, 'mysql://localhost/app') class TransitionLog include DataMapper::Resource end class Vehicle < ActiveRecord::Base include DataMapper::Resource state_machine :use_transactions => true do after_failure do |transition| DataMapper.repository(:logs) do TransitionLog.create(:vehicle => vehicle, :transition => transition) end end ... end end
The failure callback creates TransitionLog records using a second connection to the database, allowing them to be saved without being affected by rollbacks in the Vehicle resource‘s transaction.
defaults | [R] |
# File lib/state_machine/integrations/data_mapper/versions.rb, line 5 5: def self.active? 6: ::DataMapper::VERSION =~ /^0\.9\./ 7: end
# File lib/state_machine/integrations/data_mapper/versions.rb, line 15 15: def self.active? 16: ::DataMapper::VERSION =~ /^0\.\d\./ || ::DataMapper::VERSION =~ /^0\.10\./ 17: end
# File lib/state_machine/integrations/data_mapper/versions.rb, line 25 25: def self.active? 26: ::DataMapper::VERSION =~ /^0\.9\.[4-6]/ 27: end
# File lib/state_machine/integrations/data_mapper/versions.rb, line 37 37: def self.active? 38: ::DataMapper::VERSION == '1.0.0' 39: end
Whether this integration is available. Only true if DataMapper::Resource is defined.
# File lib/state_machine/integrations/data_mapper.rb, line 316 316: def self.available? 317: defined?(::DataMapper::Resource) 318: end
Should this integration be used for state machines in the given class? Classes that include DataMapper::Resource will automatically use the DataMapper integration.
# File lib/state_machine/integrations/data_mapper.rb, line 323 323: def self.matches?(klass) 324: klass <= ::DataMapper::Resource 325: end
# File lib/state_machine/integrations/data_mapper/versions.rb, line 9 9: def action_hook 10: action 11: end
0.9.4 - 0.9.6 fails to run after callbacks when validations are enabled because of the way dm-validations integrates
# File lib/state_machine/integrations/data_mapper/versions.rb, line 31 31: def define_action_helpers? 32: super if action != :save || !supports_validations? 33: end
Describes the current validation errors on the given object. If none are specific, then the default error is interpeted as a "halt".
# File lib/state_machine/integrations/data_mapper.rb, line 340 340: def errors_for(object) 341: if object.errors.empty? 342: 'Transition halted' 343: else 344: errors = [] 345: object.errors.each_pair do |field_name, field_errors| 346: field_errors.each {|error| errors << "#{field_name} #{error}"} 347: end 348: errors * ', ' 349: end 350: end
Adds a validation error to the given object
# File lib/state_machine/integrations/data_mapper.rb, line 334 334: def invalidate(object, attribute, message, values = []) 335: object.errors.add(self.attribute(attribute), generate_message(message, values)) if supports_validations? 336: end
# File lib/state_machine/integrations/data_mapper/versions.rb, line 41 41: def pluralize(word) 42: (defined?(::ActiveSupport::Inflector) ? ::ActiveSupport::Inflector : ::Extlib::Inflection).pluralize(word.to_s) 43: end
# File lib/state_machine/integrations/data_mapper/versions.rb, line 19 19: def pluralize(word) 20: ::Extlib::Inflection.pluralize(word.to_s) 21: end
Resets any errors previously added when invalidating the given object
# File lib/state_machine/integrations/data_mapper.rb, line 353 353: def reset(object) 354: object.errors.clear if supports_validations? 355: end
Uses internal save hooks if using the :save action
# File lib/state_machine/integrations/data_mapper.rb, line 419 419: def action_hook 420: action == :save ? :save_self : super 421: end
Creates a new callback in the callback chain, always ensuring that it‘s configured to bind to the object as this is the convention for DataMapper/Extlib callbacks
# File lib/state_machine/integrations/data_mapper.rb, line 444 444: def add_callback(type, options, &block) 445: options[:bind_to_object] = true 446: super 447: end
Initializes class-level extensions and defaults for this machine
# File lib/state_machine/integrations/data_mapper.rb, line 359 359: def after_initialize 360: super 361: load_observer_extensions 362: end
Creates a scope for finding records with a particular state or states for the attribute
# File lib/state_machine/integrations/data_mapper.rb, line 425 425: def create_with_scope(name) 426: lambda {|resource, values| resource.all(attribute => values)} 427: end
Creates a scope for finding records without a particular state or states for the attribute
# File lib/state_machine/integrations/data_mapper.rb, line 431 431: def create_without_scope(name) 432: lambda {|resource, values| resource.all(attribute.to_sym.not => values)} 433: end
Adds hooks into validation for automatically firing events
# File lib/state_machine/integrations/data_mapper.rb, line 405 405: def define_action_helpers 406: super 407: 408: if action == :save && supports_validations? 409: define_helper :instance, "def valid?(*)\nself.class.state_machines.transitions(self, :save, :after => false).perform { super }\nend\n", __FILE__, __LINE__ + 1 410: end 411: end
Skips defining reader/writer methods since this is done automatically
# File lib/state_machine/integrations/data_mapper.rb, line 392 392: def define_state_accessor 393: owner_class.property(attribute, String) unless owner_class.properties.detect {|property| property.name == attribute} 394: 395: if supports_validations? 396: name = self.name 397: owner_class.validates_with_block(attribute) do 398: machine = self.class.state_machine(name) 399: machine.states.match(self) ? true : [false, machine.generate_message(:invalid)] 400: end 401: end 402: 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/data_mapper.rb, line 382 382: def define_state_initializer 383: define_helper :instance, "def initialize(*args)\nself.class.state_machines.initialize_states(self) { super }\nend\n", __FILE__, __LINE__ + 1 384: end
Loads extensions to DataMapper‘s Observers
# File lib/state_machine/integrations/data_mapper.rb, line 365 365: def load_observer_extensions 366: require 'state_machine/integrations/data_mapper/observer' if ::DataMapper.const_defined?('Observer') 367: end
Pluralizes the name using the built-in inflector
# File lib/state_machine/integrations/data_mapper.rb, line 375 375: def pluralize(word) 376: ::DataMapper::Inflector.pluralize(word.to_s) 377: end
Is validation support currently loaded?
# File lib/state_machine/integrations/data_mapper.rb, line 370 370: def supports_validations? 371: @supports_validations ||= ::DataMapper.const_defined?('Validate') 372: end
Runs a new database transaction, rolling back any changes if the yielded block fails (i.e. returns false).
# File lib/state_machine/integrations/data_mapper.rb, line 437 437: def transaction(object) 438: object.class.transaction {|t| t.rollback unless yield} 439: end