### Home Classes Methods

### In Files

- lib/state_machine/integrations/sequel.rb
- lib/state_machine/integrations/sequel/versions.rb

### Methods

- ::active?
- ::matching_ancestors
- #add_callback
- #around_save
- #attribute_column
- #create_scope
- #create_with_scope
- #create_without_scope
- #define_action_helpers
- #define_action_hook
- #define_helpers
- #define_state_accessor
- #define_state_initializer
- #define_validation_hook
- #errors_for
- #handle_save_failure
- #handle_validation_failure
- #invalidate
- #load_inflector
- #load_plugins
- #model_from_dataset
- #owner_class_attribute_default
- #owner_class_attribute_default_matches?
- #pluralize
- #reset
- #run_scope
- #transaction
- #write

### 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::Sequel

Adds support for integrating state machines with Sequel models.

## Examples

Below is an example of a simple state machine defined within a Sequel model:

    class Vehicle < Sequel::Model
      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 made as well.

For example,

    vehicle = Vehicle.create          # => #<Vehicle @values={:state=>"parked", :name=>nil, :id=>1}>
    vehicle.name = 'Ford Explorer'
    vehicle.ignite                    # => true
    vehicle.refresh                   # => #<Vehicle @values={:state=>"idling", :name=>"Ford Explorer", :id=>1}>

## 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 Sequel, 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 @values={:state=>"parked", :name=>nil, :id=>1}>
    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                      # => #<Vehicle @values={:state=>"idling", :name=>nil, :id=>1}>
    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 @values={:state=>"idling", :name=>nil, :id=>1}>
    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 < Sequel::Model
      set_restricted_columns :state_event
      # set_allowed_columns ... # 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 < Sequel::Model
      set_restricted_columns :state_event # Prevent access to events in the first machine

      state_machine do
        # Define private events here
      end

      # Allow both machines to share the same state
      state_machine :public_state, :attribute => :state do
        # Define public events here
      end
    end

## Transactions

In order to ensure that any changes made during transition callbacks are rolled back during a failed attempt, every transition is wrapped within a transaction.

For example,

    class Message < Sequel::Model
    end

    Vehicle.state_machine do
      before_transition do |transition|
        Message.create(:content => transition.inspect)
        false
      end
    end

    vehicle = Vehicle.create      # => #<Vehicle @values={:state=>"parked", :name=>nil, :id=>1}>
    vehicle.ignite                # => false
    Message.count                 # => 0

Note that only before callbacks that halt the callback chain and failed attempts to save the record will result in the transaction being rolled back. If an after callback halts the chain, the previous result still applies and the transaction is not rolled back.

To turn off transactions:

    class Vehicle < Sequel::Model
      state_machine :initial => :parked, :use_transactions => false 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 @values={:state=>"parked", :name=>nil, :id=>1}>
    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 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 < Sequel::Model
      class << self
        def with_states(*states)
          filter(:state => states)
        end
        alias_method :with_state, :with_states

        def without_states(*states)
          filter(~{:state => states})
        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 Sequel, they can be chained like so:

    Vehicle.with_state(:parked).order(:id.desc)

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 Sequel resources behave in the same way that other Sequel 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 < Sequel::Model
      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.

### 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 Sequel, a save failure will cause any records that get created in your callback to roll back. You can work around this issue like so:

    DB = Sequel.connect('mysql://localhost/app')
    DB_LOGS = Sequel.connect('mysql://localhost/app')

    class TransitionLog < Sequel::Model(DB_LOGS[:transition_logs])
    end

    class Vehicle < Sequel::Model(DB[:vehicles])
      state_machine do
        after_failure do |transition|
          TransitionLog.create(:vehicle => vehicle, :transition => transition)
        end

        ...
      end
    end

The `TransitionLog` model uses a second connection to the database that allows new records to be saved without being affected by rollbacks in the `Vehicle` model's transaction.

### Callback Order

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

- (-) save

- (-) begin transaction (if enabled)

- (1) before_transition

- (2) before_validation

- (-) validate

- (3) after_validation

- (4) before_save

- (5) before_create

- (-) create

- (6) after_create

- (7) after_save

- (8) after_transition

- (-) end transaction (if enabled)

- (9) after_commit

### Public Class Methods

active?() click to toggle source

    # File lib/state_machine/integrations/sequel/versions.rb, line 5
    def self.active?
      !defined?(::Sequel::MAJOR) || ::Sequel::MAJOR == 2 || ::Sequel::MAJOR == 3 && ::Sequel::MINOR <= 23
    end

matching_ancestors() click to toggle source

Classes that include Sequel::Model will automatically use the Sequel integration.

    # File lib/state_machine/integrations/sequel.rb, line 286
    def self.matching_ancestors
      %(Sequel::Model)
    end

### Public Instance Methods

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/sequel.rb, line 310
    def errors_for(object)
      object.errors.empty? ? 'Transition halted' : object.errors.full_messages * ', '
    end

handle_validation_failure() click to toggle source

    # File lib/state_machine/integrations/sequel/versions.rb, line 51
    def handle_validation_failure
      'raise_on_save_failure ? save_failure(:validation) : result'
    end

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

Adds a validation error to the given object

    # File lib/state_machine/integrations/sequel.rb, line 304
    def invalidate(object, attribute, message, values = [])
      object.errors.add(self.attribute(attribute), generate_message(message, values))
    end

pluralize(word) click to toggle source

Pluralizes the name using the built-in inflector

    # File lib/state_machine/integrations/sequel.rb, line 320
    def pluralize(word)
      load_inflector
      super
    end

reset(object) click to toggle source

Resets any errors previously added when invalidating the given object

    # File lib/state_machine/integrations/sequel.rb, line 315
    def reset(object)
      object.errors.clear
    end

write(object, attribute, value, *args) click to toggle source

Forces the change in state to be recognized regardless of whether the state value actually changed

    # File lib/state_machine/integrations/sequel.rb, line 292
    def write(object, attribute, value, *args)
      result = super

      column = self.attribute.to_sym
      if (attribute == :state || attribute == :event && value) && owner_class.columns.include?(column) && !object.changed_columns.include?(column)
        object.changed_columns << column
      end

      result
    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 Sequel callbacks

    # File lib/state_machine/integrations/sequel.rb, line 479
    def add_callback(type, options, &block)
      options[:bind_to_object] = true
      options[:terminator] = @terminator ||= lambda {|result| result == false}
      super
    end

around_save(object) click to toggle source

Runs state events around the machine's :save action

    # File lib/state_machine/integrations/sequel.rb, line 400
    def around_save(object)
      result = transaction(object) do
        object.class.state_machines.transitions(object, action).perform { yield }
      end
      result
    end

attribute_column() click to toggle source

Generates the fully-qualifed column name for this machine's attribute

    # File lib/state_machine/integrations/sequel.rb, line 462
    def attribute_column
      ::Sequel::SQL::QualifiedIdentifier.new(owner_class.table_name, attribute)
    end

create_scope(name, scope) click to toggle source

Creates a new named scope with the given name

    # File lib/state_machine/integrations/sequel.rb, line 441
    def create_scope(name, scope)
      machine = self
      owner_class.def_dataset_method(name) do |*states|
        machine.send(:run_scope, scope, self, states)
      end

      false
    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/sequel.rb, line 430
    def create_with_scope(name)
      create_scope(name, lambda {|dataset, values| dataset.filter(attribute_column => 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/sequel.rb, line 436
    def create_without_scope(name)
      create_scope(name, lambda {|dataset, values| dataset.exclude(attribute_column => values)})
    end

define_action_helpers() click to toggle source

Defines validation hooks if the machine's action is to save the model

    # File lib/state_machine/integrations/sequel.rb, line 365
    def define_action_helpers
      super
      define_validation_hook if action == :save
    end

define_action_hook() click to toggle source

Uses around callbacks to run state events if using the :save hook

    # File lib/state_machine/integrations/sequel.rb, line 371
    def define_action_hook
      if action == :save
        define_helper :instance,               def #{action_hook}(*args)                opts = args.last.is_a?(Hash) ? args.last : {}                yielded = false                result = self.class.state_machine(#{name.inspect}).send(:around_save, self) do                  yielded = true                  super                end                                if yielded || result                  result                else                  #{handle_save_failure}                end              end, __FILE__, __LINE__ + 1
      else
        super
      end
    end

define_helpers() click to toggle source

Initializes class-level extensions for this machine

    # File lib/state_machine/integrations/sequel.rb, line 327
    def define_helpers
      load_plugins
      super
    end

define_state_accessor() click to toggle source

Skips defining reader/writer methods since this is done automatically

    # File lib/state_machine/integrations/sequel.rb, line 354
    def define_state_accessor
      define_helper :instance,             def validate(*)              super              machine = self.class.state_machine(#{name.inspect})              machine.invalidate(self, :state, :invalid) unless machine.states.match(self)            end, __FILE__, __LINE__ + 1
    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/sequel.rb, line 345
    def define_state_initializer
      define_helper :instance,             def initialize_set(*)              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/sequel.rb, line 408
    def define_validation_hook
      define_helper :instance,             def around_validation(*)              self.class.state_machines.transitions(self, :save, :after => false).perform { super }            end, __FILE__, __LINE__ + 1
    end

handle_save_failure() click to toggle source

Handles how save failures (due to invalid transitions) are raised

    # File lib/state_machine/integrations/sequel.rb, line 395
    def handle_save_failure
      'raise_hook_failure(:before_transition) if raise_on_failure?(opts)'
    end

load_inflector() click to toggle source

Loads the built-in inflector

    # File lib/state_machine/integrations/sequel.rb, line 338
    def load_inflector
      require 'sequel/extensions/inflector'
    end

load_plugins() click to toggle source

Loads all of the Sequel plugins necessary to run

    # File lib/state_machine/integrations/sequel.rb, line 333
    def load_plugins
      owner_class.plugin(:hook_class_methods)
    end

model_from_dataset(dataset) click to toggle source

Determines the model associated with the given dataset

    # File lib/state_machine/integrations/sequel.rb, line 457
    def model_from_dataset(dataset)
      dataset.model
    end

owner_class_attribute_default() click to toggle source

Gets the db default for the machine's attribute

    # File lib/state_machine/integrations/sequel.rb, line 417
    def owner_class_attribute_default
      if owner_class.db.table_exists?(owner_class.table_name) && column = owner_class.db_schema[attribute.to_sym]
        column[:default]
      end
    end

owner_class_attribute_default_matches?(state) click to toggle source

Uses the DB literal to match the default against the specified state

    # File lib/state_machine/integrations/sequel.rb, line 424
    def owner_class_attribute_default_matches?(state)
      owner_class.db.literal(state.value) == owner_class_attribute_default
    end

run_scope(scope, dataset, states) click to toggle source

Generates the results for the given scope based on one or more states to filter by

    # File lib/state_machine/integrations/sequel.rb, line 452
    def run_scope(scope, dataset, states)
      super(scope, model_from_dataset(dataset).state_machine(name), dataset, states)
    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/sequel.rb, line 468
    def transaction(object)
      result = nil
      object.db.transaction do
        raise ::Sequel::Error::Rollback unless result = yield
      end
      result
    end

[Validate]

Generated with the Darkfish Rdoc Generator 2.