### Home Classes Methods

### In Files

- lib/state_machine/integrations/data_mapper/observer.rb
- lib/state_machine/integrations/data_mapper/versions.rb
- lib/state_machine/integrations/data_mapper.rb

### Namespace

- MODULE StateMachine::Integrations::DataMapper::Observer

### Methods

- ::active?
- ::matching_ancestors
- #add_callback
- #after_initialize
- #attribute_property
- #create_with_scope
- #create_without_scope
- #define_action_helpers
- #define_action_helpers?
- #define_state_accessor
- #define_state_initializer
- #define_validation_hook
- #errors_for
- #invalidate
- #load_observer_extensions
- #owner_class_attribute_default
- #pluralize
- #reset
- #supports_validations?
- #transaction

### Included Modules

- StateMachine::Integrations::Base

### Files

- LICENSE

### Class/Module Index

Quicksearch

- StateMachine
- StateMachine::AllMatcher
- StateMachine::Assertions
- StateMachine::AttributeTransitionCollection
- StateMachine::BlacklistMatcher
- StateMachine::Branch
- StateMachine::Callback
- StateMachine::ClassMethods
- StateMachine::Error
- 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
- StateMachine::Integrations::DataMapper::Observer
- StateMachine::Integrations::MongoMapper
- StateMachine::Integrations::Mongoid
- StateMachine::Integrations::Sequel
- StateMachine::InvalidEvent
- StateMachine::InvalidParallelTransition
- StateMachine::InvalidTransition
- StateMachine::LoopbackMatcher
- StateMachine::Machine
- StateMachine::MachineCollection
- StateMachine::MacroMethods
- StateMachine::Matcher
- StateMachine::MatcherHelpers
- StateMachine::NodeCollection
- StateMachine::Path
- StateMachine::PathCollection
- StateMachine::RailsEngine
- StateMachine::State
- StateMachine::StateCollection
- StateMachine::StateContext
- StateMachine::Transition
- StateMachine::TransitionCollection
- StateMachine::WhitelistMatcher
- StateMachine::YARD
- StateMachine::YARD::Handlers
- StateMachine::YARD::Handlers::Base
- StateMachine::YARD::Handlers::Event
- StateMachine::YARD::Handlers::Machine
- StateMachine::YARD::Handlers::State
- StateMachine::YARD::Handlers::Transition
- Object

No matching classes.

# StateMachine::Integrations::DataMapper

Adds support for integrating state machines with DataMapper resources.

## Examples

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.

## Actions

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">

## 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 DataMapper, these automated events are run in the following order:

- before validation - If validation feature loaded, run before callbacks and persist new states, then validate

- before save - If validation feature was skipped/not loaded, 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                    # => #<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.

### 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 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

### Within DataMapper Hooks

DataMapper protects against the potential for system stack errors resulting from infinite loops by preventing records from being saved multiple times within save hooks. You need to be acutely aware of this when interacting with state_machine within save hooks. There are two things to keep in mind:

1. You cannot run a state_machine event during an `after :save/:create` hook.

2. If you need to run a state_machine event during a `before :save/:create/etc.` hook, then you have to force the machine's action to be skipped by passing `false` in as an argument to the event.

For example:

    class Vehicle
      include DataMapper::Resource
      ...

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

      # This will allow the event to transition without attempting to save a second time
      before :create { ignite(false) }

      # This will never work because DataMapper will refuse to save the
      # changes since we're still inside of a transaction
      # after :create { ignite }
    end

While the above will work, in reality you should typically just set the `state_event` attribute in `initialize` to automatically transition an object on creation.

## Transactions

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

## 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                  # => ["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 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')

## Callbacks / Observers

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.

### Failure callbacks

`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.

### Callback Order

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

- (-) save

- (-) begin transaction (if enabled)

- (1) before_transition

- (2) before :valid?

- (-) valid?

- (3) after :valid?

- (4) before :save

- (-) save

- (5) before :create

- (-) create

- (6) after :create

- (7) after :save

- (8) after_transition

- (-) end transaction (if enabled)

### Public Class Methods

active?() click to toggle source

    # File lib/state_machine/integrations/data_mapper/versions.rb, line 5
    def self.active?
      ::DataMapper::VERSION =~ /^0\.\d\./ || ::DataMapper::VERSION =~ /^0\.10\./
    end

matching_ancestors() click to toggle source

Classes that include DataMapper::Resource will automatically use the DataMapper integration.

    # File lib/state_machine/integrations/data_mapper.rb, line 356
    def self.matching_ancestors
      %(DataMapper::Resource)
    end

### Public Instance Methods

define_action_helpers() click to toggle source

    # File lib/state_machine/integrations/data_mapper/versions.rb, line 19
    def define_action_helpers
      if action_hook == :save
        define_helper :instance,               def save(*)                self.class.state_machines.transitions(self, :save).perform { super }              end, __FILE__, __LINE__ + 1

        define_validation_hook
      else
        super
      end
    end

define_action_helpers?() click to toggle source

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 41
    def define_action_helpers?
      super if action != :save || !supports_validations?
    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/data_mapper.rb, line 373
    def errors_for(object)
      if object.errors.empty?
        'Transition halted'
      else
        errors = []
        object.errors.each_pair do |field_name, field_errors|
          field_errors.each {|error| errors << "#{field_name} #{error}"}
        end
        errors * ', '
      end
    end

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

Adds a validation error to the given object

    # File lib/state_machine/integrations/data_mapper.rb, line 367
    def invalidate(object, attribute, message, values = [])
      object.errors.add(self.attribute(attribute), generate_message(message, values)) if supports_validations?
    end

pluralize(word) click to toggle source

    # File lib/state_machine/integrations/data_mapper/versions.rb, line 9
    def pluralize(word)
      ::Extlib::Inflection.pluralize(word.to_s)
    end

reset(object) click to toggle source

Resets any errors previously added when invalidating the given object

    # File lib/state_machine/integrations/data_mapper.rb, line 386
    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 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 505
    def add_callback(type, options, &block)
      options[:bind_to_object] = true
      super
    end

after_initialize() click to toggle source

Initializes class-level extensions and defaults for this machine

    # File lib/state_machine/integrations/data_mapper.rb, line 392
    def after_initialize
      super
      load_observer_extensions
    end

attribute_property() click to toggle source

Gets the property for this machine's attribute (if it exists)

    # File lib/state_machine/integrations/data_mapper.rb, line 413
    def attribute_property
      owner_class.properties.detect {|property| property.name == attribute}
    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/data_mapper.rb, line 486
    def create_with_scope(name)
      lambda {|resource, values| resource.all(attribute => values)}
    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/data_mapper.rb, line 492
    def create_without_scope(name)
      lambda {|resource, values| resource.all(attribute.to_sym.not => values)}
    end

define_state_accessor() click to toggle source

Skips defining reader/writer methods since this is done automatically

    # File lib/state_machine/integrations/data_mapper.rb, line 434
    def define_state_accessor
      owner_class.property(attribute, String) unless attribute_property

      if supports_validations?
        name = self.name
        owner_class.validates_with_block(attribute) do
          machine = self.class.state_machine(name)
          machine.states.match(self) ? true : [false, machine.generate_message(:invalid)]
        end
      end
    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/data_mapper.rb, line 425
    def define_state_initializer
      define_helper :instance,             def initialize(*args)              self.class.state_machines.initialize_states(self, :static => :force) { super }            end, __FILE__, __LINE__ + 1
    end

define_validation_hook() click to toggle source

Adds hooks into validation for automatically firing events

    # File lib/state_machine/integrations/data_mapper.rb, line 474
    def define_validation_hook
      if supports_validations?
        define_helper :instance,               def valid?(*)                self.class.state_machines.transitions(self, :save, :after => false).perform { super }              end, __FILE__, __LINE__ + 1
      end
    end

load_observer_extensions() click to toggle source

Loads extensions to DataMapper's Observers

    # File lib/state_machine/integrations/data_mapper.rb, line 398
    def load_observer_extensions
      require 'state_machine/integrations/data_mapper/observer' if ::DataMapper.const_defined?('Observer')
    end

owner_class_attribute_default() click to toggle source

Gets the db default for the machine's attribute

    # File lib/state_machine/integrations/data_mapper.rb, line 408
    def owner_class_attribute_default
      attribute_property && attribute_property.default
    end

supports_validations?() click to toggle source

Is validation support currently loaded?

    # File lib/state_machine/integrations/data_mapper.rb, line 403
    def supports_validations?
      @supports_validations ||= ::DataMapper.const_defined?('Validate')
    end

transaction(object) click to toggle source

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 498
    def transaction(object)
      object.class.transaction {|t| t.rollback unless yield}
    end

[Validate]

Generated with the Darkfish Rdoc Generator 2.