### Home Classes Methods

### In Files

- lib/state_machine/integrations/active_model/observer_update.rb
- lib/state_machine/integrations/active_model/observer.rb
- lib/state_machine/integrations/active_model/versions.rb
- lib/state_machine/integrations/active_model.rb

### Namespace

- MODULE StateMachine::Integrations::ActiveModel::Observer
- CLASS StateMachine::Integrations::ActiveModel::ObserverUpdate

### Methods

- ::active?
- ::matching_ancestors
- #add_callback
- #add_default_callbacks
- #add_events
- #add_states
- #after_initialize
- #ancestors_for
- #around_validation
- #callback_terminator
- #default_error_message_options
- #define_action_helpers
- #define_state_accessor
- #define_validation_hook
- #errors_for
- #i18n_scope
- #invalidate
- #load_locale
- #load_observer_extensions
- #notify
- #reset
- #runs_validations_on_action?
- #supports_observers?
- #supports_validations?
- #translate

### Included Modules

- StateMachine::Integrations::Base

### Files

- LICENSE

### Class/Module Index

Quicksearch

- StateMachine
- StateMachine::AllMatcher
- StateMachine::Assertions
- StateMachine::AttributeTransitionCollection
- StateMachine::BlacklistMatcher
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- StateMachine::Callback
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- StateMachine::EvalHelpers
- StateMachine::Event
- StateMachine::EventCollection
- StateMachine::Graph
- StateMachine::InstanceMethods
- StateMachine::IntegrationNotFound
- StateMachine::Integrations
- StateMachine::Integrations::ActiveModel
- StateMachine::Integrations::ActiveModel::Observer
- StateMachine::Integrations::ActiveModel::ObserverUpdate
- StateMachine::Integrations::ActiveRecord
- StateMachine::Integrations::Base
- StateMachine::Integrations::Base::ClassMethods
- StateMachine::Integrations::DataMapper
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- StateMachine::InvalidEvent
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- StateMachine::LoopbackMatcher
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- StateMachine::TransitionCollection
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- StateMachine::YARD::Handlers::Machine
- StateMachine::YARD::Handlers::State
- StateMachine::YARD::Handlers::Transition
- Object

No matching classes.

# StateMachine::Integrations::ActiveModel

Adds support for integrating state machines with ActiveModel classes.

## Examples

If using ActiveModel directly within your class, then any one of the following features need to be included in order for the integration to be detected:

- ActiveModel::Observing

- ActiveModel::Validations

Below is an example of a simple state machine defined within an ActiveModel class:

    class Vehicle
      include ActiveModel::Observing
      include ActiveModel::Validations

      attr_accessor :state
      define_attribute_methods [:state]

      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, no action will be invoked when a state is transitioned. This means that if you want to save changes when transitioning, you must define the action yourself like so:

    class Vehicle
      include ActiveModel::Validations
      attr_accessor :state

      state_machine :action => :save do
        ...
      end

      def save
        # Save changes
      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 ActiveModel's validation framework, custom validators will not work as expected when defined to run in multiple states. For example:

    class Vehicle
      include ActiveModel::Validations

      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 ActiveModel::Validations

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

## Validation errors

In order to hook in validation support for your model, the ActiveModel::Validations feature must be included. If this is included and an event fails to successfully fire because there are no matching transitions for the object, a validation error is added to the object's state attribute to help in determining why it failed.

For example,

    vehicle = Vehicle.new
    vehicle.ignite                # => false
    vehicle.errors.full_messages  # => ["State cannot transition via \"ignite\""]

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)

### 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 ActiveModel::MassAssignmentSecurity
      attr_accessor :state

      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 ActiveModel::MassAssignmentSecurity
      attr_accessor :state

      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

## Callbacks

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

For example,

    class Vehicle
      include ActiveModel::Validations
      attr_accessor :state

      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.

## Observers

In order to hook in observer support for your application, the ActiveModel::Observing feature must be included. Because of the way ActiveModel observers are designed, there is less flexibility around the specific transitions that can be hooked in. However, a large number of hooks are supported. For example, if a transition for a object's `state` attribute changes the state from `parked` to `idling` via the `ignite` event, the following observer methods are supported:

- before/after/after_failure_to-_ignite_from_parked_to_idling

- before/after/after_failure_to-_ignite_from_parked

- before/after/after_failure_to-_ignite_to_idling

- before/after/after_failure_to-_ignite

- before/after/after_failure_to-_transition_state_from_parked_to_idling

- before/after/after_failure_to-_transition_state_from_parked

- before/after/after_failure_to-_transition_state_to_idling

- before/after/after_failure_to-_transition_state

- before/after/after_failure_to-_transition

The following class shows an example of some of these hooks:

    class VehicleObserver < ActiveModel::Observer
      # Callback for :ignite event *before* the transition is performed
      def before_ignite(vehicle, transition)
        # log message
      end

      # Callback for :ignite event *after* the transition has been performed
      def after_ignite(vehicle, transition)
        # put on seatbelt
      end

      # Generic transition callback *before* the transition is performed
      def after_transition(vehicle, transition)
        Audit.log(vehicle, transition)
      end

      def after_failure_to_transition(vehicle, transition)
        Audit.error(vehicle, transition)
      end
    end

More flexible transition callbacks can be defined directly within the model as described in StateMachine::Machine#before_transition and StateMachine::Machine#after_transition.

To define a single observer for multiple state machines:

    class StateMachineObserver < ActiveModel::Observer
      observe Vehicle, Switch, Project

      def after_transition(object, transition)
        Audit.log(object, transition)
      end
    end

## Internationalization

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

    en:
      activemodel:
        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:
      activemodel:
        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":

- `activemodel.state_machines.#{model_name}.#{machine_name}.states.#{state_name}`

- `activemodel.state_machines.#{model_name}.states.#{state_name}`

- `activemodel.state_machines.#{machine_name}.states.#{state_name}`

- `activemodel.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":

- `activemodel.state_machines.#{model_name}.#{machine_name}.events.#{event_name}`

- `activemodel.state_machines.#{model_name}.events.#{event_name}`

- `activemodel.state_machines.#{machine_name}.events.#{event_name}`

- `activemodel.state_machines.events.#{event_name}`

An example translation configuration might look like so:

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

## Dirty Attribute Tracking

When using the ActiveModel::Dirty extension, your model will keep track of any changes that are made to attributes. Depending on your ORM, an object will only be saved when there are attributes that have changed on the object. When integrating with state_machine, typically the `state` field will be marked as dirty after a transition occurs. In some situations, however, this isn't the case.

If you define loopback transitions in your state machine, the value for the machine's attribute (e.g. state) will not change. Unless you explicitly indicate so, this means that your object won't persist anything on a loopback. For example:

    class Vehicle
      include ActiveModel::Validations
      include ActiveModel::Dirty
      attr_accessor :state

      state_machine :initial => :parked do
        event :park do
          transition :parked => :parked, ...
        end
      end
    end

If, instead, you'd like your object to always persist regardless of whether the value actually changed, you can do so by using the `#{attribute}_will_change!` helpers or defining a `before_transition` callback that actually changes an attribute on the model. For example:

    class Vehicle
      ...
      state_machine :initial => :parked do
        before_transition all => same do |vehicle|
          vehicle.state_will_change!

          # Alternative solution, updating timestamp
          # vehicle.updated_at = Time.curent
        end
      end
    end

## Creating new integrations

If you want to integrate state_machine with an ORM that implements parts or all of the ActiveModel API, only the machine defaults need to be specified. Otherwise, the implementation is similar to any other integration.

For example,

    module StateMachine::Integrations::MyORM
      include StateMachine::Integrations::ActiveModel

      @defaults = {:action = > :persist}

      def self.matches?(klass)
        defined?(::MyORM::Base) && klass <= ::MyORM::Base
      end

      protected
        def runs_validations_on_action?
          action == :persist
        end
    end

If you wish to implement other features, such as attribute initialization with protected attributes, named scopes, or database transactions, you must add these independent of the ActiveModel integration. See the ActiveRecord implementation for examples of these customizations.

### Public Class Methods

active?() click to toggle source

    # File lib/state_machine/integrations/active_model/versions.rb, line 5
    def self.active?
      !defined?(::ActiveModel::VERSION) || ::ActiveModel::VERSION::MAJOR == 2
    end

matching_ancestors() click to toggle source

Classes that include ActiveModel::Observing or ActiveModel::Validations will automatically use the ActiveModel integration.

    # File lib/state_machine/integrations/active_model.rb, line 371
    def self.matching_ancestors
      %(ActiveModel ActiveModel::Observing ActiveModel::Validations)
    end

### Public Instance Methods

define_validation_hook() click to toggle source

    # File lib/state_machine/integrations/active_model/versions.rb, line 9
    def define_validation_hook
      define_helper :instance,             def valid?(*)              self.class.state_machines.transitions(self, #{action.inspect}, :after => false).perform { super }            end, __FILE__, __LINE__ + 1
    end

errors_for(object) click to toggle source

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/active_model.rb, line 391
    def errors_for(object)
      object.errors.empty? ? 'Transition halted' : object.errors.full_messages * ', '
    end

invalidate(object, attribute, message, values = []) click to toggle source

Adds a validation error to the given object

    # File lib/state_machine/integrations/active_model.rb, line 376
    def invalidate(object, attribute, message, values = [])
      if supports_validations?
        attribute = self.attribute(attribute)
        options = values.inject({}) do |h, (key, value)|
          h[key] = value
          h
        end

        default_options = default_error_message_options(object, attribute, message)
        object.errors.add(attribute, message, options.merge(default_options))
      end
    end

reset(object) click to toggle source

Resets any errors previously added when invalidating the given object

    # File lib/state_machine/integrations/active_model.rb, line 396
    def reset(object)
      object.errors.clear if supports_validations?
    end

### Protected Instance Methods

add_callback(type, options, &block) click to toggle source

Creates a new callback in the callback chain, always inserting it before the default Observer callbacks that were created after initialization.

    # File lib/state_machine/integrations/active_model.rb, line 520
    def add_callback(type, options, &block)
      options[:terminator] = callback_terminator

      if supports_observers?
        @callbacks[type == :around ? :before : type].insert(-2, callback = Callback.new(type, options, &block))
        add_states(callback.known_states)
        callback
      else
        super
      end
    end

add_default_callbacks() click to toggle source

Adds a set of default callbacks that utilize the Observer extensions

    # File lib/state_machine/integrations/active_model.rb, line 482
    def add_default_callbacks
      if supports_observers?
        callbacks[:before] << Callback.new(:before) {|object, transition| notify(:before, object, transition)}
        callbacks[:after] << Callback.new(:after) {|object, transition| notify(:after, object, transition)}
        callbacks[:failure] << Callback.new(:failure) {|object, transition| notify(:after_failure_to, object, transition)}
      end
    end

add_events(new_events) click to toggle source

Configures new event with the built-in humanize scheme

    # File lib/state_machine/integrations/active_model.rb, line 540
    def add_events(new_events)
      super.each do |new_event|
        new_event.human_name = lambda {|event, klass| translate(klass, :event, event.name)}
      end
    end

add_states(new_states) click to toggle source

Configures new states with the built-in humanize scheme

    # File lib/state_machine/integrations/active_model.rb, line 533
    def add_states(new_states)
      super.each do |new_state|
        new_state.human_name = lambda {|state, klass| translate(klass, :state, state.name)}
      end
    end

after_initialize() click to toggle source

Initializes class-level extensions and defaults for this machine

    # File lib/state_machine/integrations/active_model.rb, line 463
    def after_initialize
      super
      load_locale
      load_observer_extensions
      add_default_callbacks
    end

ancestors_for(klass) click to toggle source

Build a list of ancestors for the given class to use when determining which localization key to use for a particular string.

    # File lib/state_machine/integrations/active_model.rb, line 458
    def ancestors_for(klass)
      klass.lookup_ancestors
    end

around_validation(object) click to toggle source

Runs state events around the object's validation process

    # File lib/state_machine/integrations/active_model.rb, line 513
    def around_validation(object)
      object.class.state_machines.transitions(object, action, :after => false).perform { yield }
    end

callback_terminator() click to toggle source

Gets the terminator to use for callbacks

    # File lib/state_machine/integrations/active_model.rb, line 421
    def callback_terminator
      @terminator ||= lambda {|result| result == false}
    end

default_error_message_options(object, attribute, message) click to toggle source

The default options to use when generating messages for validation errors

    # File lib/state_machine/integrations/active_model.rb, line 432
    def default_error_message_options(object, attribute, message)
      {:message => @messages[message]}
    end

define_action_helpers() click to toggle source

Adds hooks into validation for automatically firing events

    # File lib/state_machine/integrations/active_model.rb, line 501
    def define_action_helpers
      super
      define_validation_hook if runs_validations_on_action?
    end

define_state_accessor() click to toggle source

Skips defining reader/writer methods since this is done automatically

    # File lib/state_machine/integrations/active_model.rb, line 491
    def define_state_accessor
      name = self.name

      owner_class.validates_each(attribute) do |object, attr, value|
        machine = object.class.state_machine(name)
        machine.invalidate(object, :state, :invalid) unless machine.states.match(object)
      end if supports_validations?
    end

i18n_scope(klass) click to toggle source

Determines the base scope to use when looking up translations

    # File lib/state_machine/integrations/active_model.rb, line 426
    def i18n_scope(klass)
      klass.i18n_scope
    end

load_locale() click to toggle source

Loads any locale files needed for translating validation errors

    # File lib/state_machine/integrations/active_model.rb, line 471
    def load_locale
      I18n.load_path.unshift(@integration.locale_path) unless I18n.load_path.include?(@integration.locale_path)
    end

load_observer_extensions() click to toggle source

Loads extensions to ActiveModel's Observers

    # File lib/state_machine/integrations/active_model.rb, line 476
    def load_observer_extensions
      require 'state_machine/integrations/active_model/observer'
      require 'state_machine/integrations/active_model/observer_update'
    end

notify(type, object, transition) click to toggle source

Notifies observers on the given object that a callback occurred involving the given transition. This will attempt to call the following methods on observers:

- `#{type}_#{qualified_event}from#{from}to#{to}`

- `#{type}_#{qualified_event}from#{from}`

- `#{type}_#{qualified_event}to#{to}`

- `#{type}_#{qualified_event}`

- `#{type}transition#{machine_name}from#{from}to#{to}`

- `#{type}transition#{machine_name}from#{from}`

- `#{type}transition#{machine_name}to#{to}`

- `#{type}transition#{machine_name}`

- `#{type}_transition`

This will always return true regardless of the results of the callbacks.

    # File lib/state_machine/integrations/active_model.rb, line 561
    def notify(type, object, transition)
      name = self.name
      event = transition.qualified_event
      from = transition.from_name || 'nil'
      to = transition.to_name || 'nil'

      # Machine-specific updates
      ["#{type}_#{event}", "#{type}_transition_#{name}"].each do |event_segment|
        ["_from_#{from}", nil].each do |from_segment|
          ["_to_#{to}", nil].each do |to_segment|
            object.class.changed if object.class.respond_to?(:changed)
            object.class.notify_observers('update_with_transition', ObserverUpdate.new([event_segment, from_segment, to_segment].join, object, transition))
          end
        end
      end

      # Generic updates
      object.class.changed if object.class.respond_to?(:changed)
      object.class.notify_observers('update_with_transition', ObserverUpdate.new("#{type}_transition", object, transition))

      true
    end

runs_validations_on_action?() click to toggle source

Do validations run when the action configured this machine is invoked? This is used to determine whether to fire off attribute-based event transitions when the action is run.

    # File lib/state_machine/integrations/active_model.rb, line 416
    def runs_validations_on_action?
      false
    end

supports_observers?() click to toggle source

Whether observers are supported in the integration. Only true if ActiveModel::Observer is available.

    # File lib/state_machine/integrations/active_model.rb, line 403
    def supports_observers?
      defined?(::ActiveModel::Observing) && owner_class <= ::ActiveModel::Observing
    end

supports_validations?() click to toggle source

Whether validations are supported in the integration. Only true if the ActiveModel feature is enabled on the owner class.

    # File lib/state_machine/integrations/active_model.rb, line 409
    def supports_validations?
      defined?(::ActiveModel::Validations) && owner_class <= ::ActiveModel::Validations
    end

translate(klass, key, value) click to toggle source

Translates the given key / value combo. Translation keys are looked up in the following order:

- `#{i18n_scope}.state_machines.#{model_name}.#{machine_name}.#{plural_key}.#{value}`

- `#{i18n_scope}.state_machines.#{model_name}.#{plural_key}.#{value}`

- `#{i18n_scope}.state_machines.#{machine_name}.#{plural_key}.#{value}`

- `#{i18n_scope}.state_machines.#{plural_key}.#{value}`

If no keys are found, then the humanized value will be the fallback.

    # File lib/state_machine/integrations/active_model.rb, line 444
    def translate(klass, key, value)
      ancestors = ancestors_for(klass)
      group = key.to_s.pluralize
      value = value ? value.to_s : 'nil'

      # Generate all possible translation keys
      translations = ancestors.map {|ancestor| :"#{ancestor.model_name.to_s.underscore}.#{name}.#{group}.#{value}"}
      translations.concat(ancestors.map {|ancestor| :"#{ancestor.model_name.to_s.underscore}.#{group}.#{value}"})
      translations.concat([:"#{name}.#{group}.#{value}", :"#{group}.#{value}", value.humanize.downcase])
      I18n.translate(translations.shift, :default => translations, :scope => [i18n_scope(klass), :state_machines])
    end

[Validate]

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