require 'state_machine/machine'
# A state machine is a model of behavior composed of states, events, and
# transitions. This helper adds support for defining this type of
# functionality on any Ruby class.
module StateMachine
module MacroMethods
# Creates a new state machine with the given name. The default name, if not
# specified, is :state.
#
# Configuration options:
# * :attribute - The name of the attribute to store the state value
# in. By default, this is the same as the name of the machine.
# * :initial - The initial state of the attribute. This can be a
# static state or a lambda block which will be evaluated at runtime
# (e.g. lambda {|vehicle| vehicle.speed == 0 ? :parked : :idling}).
# Default is nil.
# * :initialize - Whether to automatically initialize the attribute
# by hooking into #initialize on the owner class. Default is true.
# * :action - The instance method to invoke when an object
# transitions. Default is nil unless otherwise specified by the
# configured integration.
# * :namespace - The name to use for namespacing all generated
# state / event instance methods (e.g. "heater" would generate
# :turn_on_heater and :turn_off_heater for the :turn_on/:turn_off events).
# Default is nil.
# * :integration - The name of the integration to use for adding
# library-specific behavior to the machine. Built-in integrations
# include :active_model, :active_record, :data_mapper, :mongo_mapper, and
# :sequel. By default, this is determined automatically.
#
# Configuration options relevant to ORM integrations:
# * :plural - The pluralized version of the name. By default, this
# will attempt to call +pluralize+ on the name. If this method is not
# available, an "s" is appended. This is used for generating scopes.
# * :messages - The error messages to use when invalidating
# objects due to failed transitions. Messages include:
# * :invalid
# * :invalid_event
# * :invalid_transition
# * :use_transactions - Whether transactions should be used when
# firing events. Default is true unless otherwise specified by the
# configured integration.
#
# This also expects a block which will be used to actually configure the
# states, events and transitions for the state machine. *Note* that this
# block will be executed within the context of the state machine. As a
# result, you will not be able to access any class methods unless you refer
# to them directly (i.e. specifying the class name).
#
# For examples on the types of state machine configurations and blocks, see
# the section below.
#
# == Examples
#
# With the default name/attribute and no configuration:
#
# class Vehicle
# state_machine do
# event :park do
# ...
# end
# end
# end
#
# The above example will define a state machine named "state" that will
# store the value in the +state+ attribute. Every vehicle will start
# without an initial state.
#
# With a custom name / attribute:
#
# class Vehicle
# state_machine :status, :attribute => :status_value do
# ...
# end
# end
#
# With a static initial state:
#
# class Vehicle
# state_machine :status, :initial => :parked do
# ...
# end
# end
#
# With a dynamic initial state:
#
# class Vehicle
# state_machine :status, :initial => lambda {|vehicle| vehicle.speed == 0 ? :parked : :idling} do
# ...
# end
# end
#
# == Class Methods
#
# The following class methods will be automatically generated by the
# state machine based on the *name* of the machine. Any existing methods
# will not be overwritten.
# * human_state_name(state) - Gets the humanized value for the
# given state. This may be generated by internationalization libraries if
# supported by the integration.
# * human_state_event_name(event) - Gets the humanized value for
# the given event. This may be generated by internationalization
# libraries if supported by the integration.
#
# For example,
#
# class Vehicle
# state_machine :state, :initial => :parked do
# event :ignite do
# transition :parked => :idling
# end
#
# event :shift_up do
# transition :idling => :first_gear
# end
# end
# end
#
# Vehicle.human_state_name(:parked) # => "parked"
# Vehicle.human_state_name(:first_gear) # => "first gear"
# Vehicle.human_state_event_name(:park) # => "park"
# Vehicle.human_state_event_name(:shift_up) # => "shift up"
#
# == Instance Methods
#
# The following instance methods will be automatically generated by the
# state machine based on the *name* of the machine. Any existing methods
# will not be overwritten.
# * state - Gets the current value for the attribute
# * state=(value) - Sets the current value for the attribute
# * state?(name) - Checks the given state name against the current
# state. If the name is not a known state, then an ArgumentError is raised.
# * state_name - Gets the name of the state for the current value
# * human_state_name - Gets the human-readable name of the state
# for the current value
# * state_events(requirements = {}) - Gets the list of events that
# can be fired on the current object's state (uses the *unqualified* event
# names)
# * state_transitions(requirements = {}) - Gets the list of
# transitions that can be made on the current object's state
# * state_paths(requirements = {}) - Gets the list of sequences of
# transitions that can be run from the current object's state
#
# The state_events, state_transitions, and state_paths
# helpers all take an optional set of requirements for determining what's
# available for the current object. These requirements include:
# * :from - One or more states to transition from. If none are
# specified, then this will be the object's current state.
# * :to - One or more states to transition to. If none are
# specified, then this will match any to state.
# * :on - One or more events to transition on. If none are
# specified, then this will match any event.
# * :guard - Whether to guard transitions with the if/unless
# conditionals defined for each one. Default is true.
#
# For example,
#
# class Vehicle
# state_machine :state, :initial => :parked do
# event :ignite do
# transition :parked => :idling
# end
#
# event :park do
# transition :idling => :parked
# end
# end
# end
#
# vehicle = Vehicle.new
# vehicle.state # => "parked"
# vehicle.state_name # => :parked
# vehicle.human_state_name # => "parked"
# vehicle.state?(:parked) # => true
#
# # Changing state
# vehicle.state = 'idling'
# vehicle.state # => "idling"
# vehicle.state_name # => :idling
# vehicle.state?(:parked) # => false
#
# # Getting current event / transition availability
# vehicle.state_events # => [:park]
# vehicle.park # => true
# vehicle.state_events # => [:ignite]
# vehicle.state_events(:from => :idling) # => [:park]
# vehicle.state_events(:to => :parked) # => []
#
# vehicle.state_transitions # => [#]
# vehicle.ignite
# vehicle.state_transitions # => [#]
#
# vehicle.state_transitions(:on => :ignite) # => []
#
# # Getting current path availability
# vehicle.state_paths # => [
# # [#,
# # #]
# # ]
# vehicle.state_paths(:guard => false) # =>
# # [#,
# # #]
# # ]
#
# == Attribute initialization
#
# For most classes, the initial values for state machine attributes are
# automatically assigned when a new object is created. However, this
# behavior will *not* work if the class defines an +initialize+ method
# without properly calling +super+.
#
# For example,
#
# class Vehicle
# state_machine :state, :initial => :parked do
# ...
# end
# end
#
# vehicle = Vehicle.new # => #
# vehicle.state # => "parked"
#
# In the above example, no +initialize+ method is defined. As a result,
# the default behavior of initializing the state machine attributes is used.
#
# In the following example, a custom +initialize+ method is defined:
#
# class Vehicle
# state_machine :state, :initial => :parked do
# ...
# end
#
# def initialize
# end
# end
#
# vehicle = Vehicle.new # => #
# vehicle.state # => nil
#
# Since the +initialize+ method is defined, the state machine attributes
# never get initialized. In order to ensure that all initialization hooks
# are called, the custom method *must* call +super+ without any arguments
# like so:
#
# class Vehicle
# state_machine :state, :initial => :parked do
# ...
# end
#
# def initialize(attributes = {})
# ...
# super()
# end
# end
#
# vehicle = Vehicle.new # => #
# vehicle.state # => "parked"
#
# Because of the way the inclusion of modules works in Ruby, calling
# super() will not only call the superclass's +initialize+, but
# also +initialize+ on all included modules. This allows the original state
# machine hook to get called properly.
#
# If you want to avoid calling the superclass's constructor, but still want
# to initialize the state machine attributes:
#
# class Vehicle
# state_machine :state, :initial => :parked do
# ...
# end
#
# def initialize(attributes = {})
# ...
# initialize_state_machines
# end
# end
#
# vehicle = Vehicle.new # => #
# vehicle.state # => "parked"
#
# == States
#
# All of the valid states for the machine are automatically tracked based
# on the events, transitions, and callbacks defined for the machine. If
# there are additional states that are never referenced, these should be
# explicitly added using the StateMachine::Machine#state or
# StateMachine::Machine#other_states helpers.
#
# When a new state is defined, a predicate method for that state is
# generated on the class. For example,
#
# class Vehicle
# state_machine :initial => :parked do
# event :ignite do
# transition all => :idling
# end
# end
# end
#
# ...will generate the following instance methods (assuming they're not
# already defined in the class):
# * parked?
# * idling?
#
# Each predicate method will return true if it matches the object's
# current state. Otherwise, it will return false.
#
# == Events and Transitions
#
# Events defined on the machine are the interface to transitioning states
# for an object. Events can be fired either directly (through the method
# generated for the event) or indirectly (through attributes defined on
# the machine).
#
# For example,
#
# class Vehicle
# include DataMapper::Resource
# property :id, Serial
#
# state_machine :initial => :parked do
# event :ignite do
# transition :parked => :idling
# end
# end
#
# state_machine :alarm_state, :initial => :active do
# event :disable do
# transition all => :off
# end
# end
# end
#
# # Fire +ignite+ event directly
# vehicle = Vehicle.create # => #
# vehicle.ignite # => true
# vehicle.state # => "idling"
# vehicle.alarm_state # => "active"
#
# # Fire +disable+ event automatically
# vehicle.alarm_state_event = 'disable'
# vehicle.save # => true
# vehicle.alarm_state # => "off"
#
# In the above example, the +state+ attribute is transitioned using the
# +ignite+ action that's generated from the state machine. On the other
# hand, the +alarm_state+ attribute is transitioned using the +alarm_state_event+
# attribute that automatically gets fired when the machine's action (+save+)
# is invoked.
#
# For more information about how to configure an event and its associated
# transitions, see StateMachine::Machine#event.
#
# == Defining callbacks
#
# Within the +state_machine+ block, you can also define callbacks for
# transitions. For more information about defining these callbacks,
# see StateMachine::Machine#before_transition, StateMachine::Machine#after_transition,
# and StateMachine::Machine#around_transition, and StateMachine::Machine#after_failure.
#
# == Namespaces
#
# When a namespace is configured for a state machine, the name provided
# will be used in generating the instance methods for interacting with
# states/events in the machine. This is particularly useful when a class
# has multiple state machines and it would be difficult to differentiate
# between the various states / events.
#
# For example,
#
# class Vehicle
# state_machine :heater_state, :initial => :off, :namespace => 'heater' do
# event :turn_on do
# transition all => :on
# end
#
# event :turn_off do
# transition all => :off
# end
# end
#
# state_machine :alarm_state, :initial => :active, :namespace => 'alarm' do
# event :turn_on do
# transition all => :active
# end
#
# event :turn_off do
# transition all => :off
# end
# end
# end
#
# The above class defines two state machines: +heater_state+ and +alarm_state+.
# For the +heater_state+ machine, the following methods are generated since
# it's namespaced by "heater":
# * can_turn_on_heater?
# * turn_on_heater
# * ...
# * can_turn_off_heater?
# * turn_off_heater
# * ..
# * heater_off?
# * heater_on?
#
# As shown, each method is unique to the state machine so that the states
# and events don't conflict. The same goes for the +alarm_state+ machine:
# * can_turn_on_alarm?
# * turn_on_alarm
# * ...
# * can_turn_off_alarm?
# * turn_off_alarm
# * ..
# * alarm_active?
# * alarm_off?
#
# == Scopes
#
# For integrations that support it, a group of default scope filters will
# be automatically created for assisting in finding objects that have the
# attribute set to one of a given set of states.
#
# For example,
#
# Vehicle.with_state(:parked) # => All vehicles where the state is parked
# Vehicle.with_states(:parked, :idling) # => All vehicles where the state is either parked or idling
#
# Vehicle.without_state(:parked) # => All vehicles where the state is *not* parked
# Vehicle.without_states(:parked, :idling) # => All vehicles where the state is *not* parked or idling
#
# *Note* that if class methods already exist with those names (i.e.
# :with_state, :with_states, :without_state, or :without_states), then a
# scope will not be defined for that name.
#
# See StateMachine::Machine for more information about using integrations
# and the individual integration docs for information about the actual
# scopes that are generated.
def state_machine(*args, &block)
StateMachine::Machine.find_or_create(self, *args, &block)
end
end
end
Class.class_eval do
include StateMachine::MacroMethods
end
require 'state_machine/initializers'