Class | StateMachine::Machine |
In: |
lib/state_machine/machine.rb
|
Parent: | Object |
Represents a state machine for a particular attribute. State machines consist of states, events and a set of transitions that define how the state changes after a particular event is fired.
A state machine will not know all of the possible states for an object unless they are referenced somewhere in the state machine definition. As a result, any unused states should be defined with the other_states or state helper.
When an action is configured for a state machine, it is invoked when an object transitions via an event. The success of the event becomes dependent on the success of the action. If the action is successful, then the transitioned state remains persisted. However, if the action fails (by returning false), the transitioned state will be rolled back.
For example,
class Vehicle attr_accessor :fail, :saving_state state_machine :initial => :parked, :action => :save do event :ignite do transition :parked => :idling end event :park do transition :idling => :parked end end def save @saving_state = state fail != true end end vehicle = Vehicle.new # => #<Vehicle:0xb7c27024 @state="parked"> vehicle.save # => true vehicle.saving_state # => "parked" # The state was "parked" was save was called # Successful event vehicle.ignite # => true vehicle.saving_state # => "idling" # The state was "idling" when save was called vehicle.state # => "idling" # Failed event vehicle.fail = true vehicle.park # => false vehicle.saving_state # => "parked" vehicle.state # => "idling"
As shown, even though the state is set prior to calling the save action on the object, it will be rolled back to the original state if the action fails. Note that this will also be the case if an exception is raised while calling the action.
In addition to the action being run as the result of an event, the action can also be used to run events itself. For example, using the above as an example:
vehicle = Vehicle.new # => #<Vehicle:0xb7c27024 @state="parked"> vehicle.state_event = 'ignite' vehicle.save # => true vehicle.state # => "idling" vehicle.state_event # => nil
As can be seen, the save action automatically invokes the event stored in the state_event attribute (:ignite in this case).
One important note about using this technique for running transitions is that if the class in which the state machine is defined also defines the action being invoked (and not a superclass), then it must manually run the StateMachine hook that checks for event attributes.
For example, in ActiveRecord, DataMapper, Mongoid, MongoMapper, and Sequel, the default action (save) is already defined in a base class. As a result, when a state machine is defined in a model / resource, StateMachine can automatically hook into the save action.
On the other hand, the Vehicle class from above defined its own save method (and there is no save method in its superclass). As a result, it must be modified like so:
def save self.class.state_machines.transitions(self, :save).perform do @saving_state = state fail != true end end
This will add in the functionality for firing the event stored in the state_event attribute.
Callbacks are supported for hooking before and after every possible transition in the machine. Each callback is invoked in the order in which it was defined. See StateMachine::Machine#before_transition and StateMachine::Machine#after_transition for documentation on how to define new callbacks.
Note that callbacks only get executed within the context of an event. As a result, if a class has an initial state when it‘s created, any callbacks that would normally get executed when the object enters that state will not get triggered.
For example,
class Vehicle state_machine :initial => :parked do after_transition all => :parked do raise ArgumentError end ... end end vehicle = Vehicle.new # => #<Vehicle id: 1, state: "parked"> vehicle.save # => true (no exception raised)
If you need callbacks to get triggered when an object is created, this should be done by one of the following techniques:
class Vehicle before :create, :track_initial_transition state_machine do ... end end
class Vehicle state_machine :initial => :pending after_transition :pending => :parked, :do => :track_initial_transition event :park do transition :pending => :parked end state :pending, :value => nil end end vehicle = Vehicle.new vehicle.park
class Vehicle < ActiveRecord::Base state_machine :initial => :pending after_transition :pending => :parked, :do => :track_initial_transition event :park do transition :pending => :parked end state :pending, :value => nil end def initialize(*) super self.state_event = 'park' end end vehicle = Vehicle.new vehicle.save
Callbacks can be canceled by throwing :halt at any point during the callback. For example,
... throw :halt ...
If a before callback halts the chain, the associated transition and all later callbacks are canceled. If an after callback halts the chain, the later callbacks are canceled, but the transition is still successful.
These same rules apply to around callbacks with the exception that any around callback that doesn‘t yield will essentially result in :halt being thrown. Any code executed after the yield will behave in the same way as after callbacks.
Note that if a before callback fails and the bang version of an event was invoked, an exception will be raised instead of returning false. For example,
class Vehicle state_machine :initial => :parked do before_transition any => :idling, :do => lambda {|vehicle| throw :halt} ... end end vehicle = Vehicle.new vehicle.park # => false vehicle.park! # => StateMachine::InvalidTransition: Cannot transition state via :park from "idling"
Observers, in the sense of external classes and not Ruby‘s Observable mechanism, can hook into state machines as well. Such observers use the same callback api that‘s used internally.
Below are examples of defining observers for the following state machine:
class Vehicle state_machine do event :park do transition :idling => :parked end ... end ... end
Event/Transition behaviors:
class VehicleObserver def self.before_park(vehicle, transition) logger.info "#{vehicle} instructed to park... state is: #{transition.from}, state will be: #{transition.to}" end def self.after_park(vehicle, transition, result) logger.info "#{vehicle} instructed to park... state was: #{transition.from}, state is: #{transition.to}" end def self.before_transition(vehicle, transition) logger.info "#{vehicle} instructed to #{transition.event}... #{transition.attribute} is: #{transition.from}, #{transition.attribute} will be: #{transition.to}" end def self.after_transition(vehicle, transition) logger.info "#{vehicle} instructed to #{transition.event}... #{transition.attribute} was: #{transition.from}, #{transition.attribute} is: #{transition.to}" end def self.around_transition(vehicle, transition) logger.info Benchmark.measure { yield } end end Vehicle.state_machine do before_transition :on => :park, :do => VehicleObserver.method(:before_park) before_transition VehicleObserver.method(:before_transition) after_transition :on => :park, :do => VehicleObserver.method(:after_park) after_transition VehicleObserver.method(:after_transition) around_transition VehicleObserver.method(:around_transition) end
One common callback is to record transitions for all models in the system for auditing/debugging purposes. Below is an example of an observer that can easily automate this process for all models:
class StateMachineObserver def self.before_transition(object, transition) Audit.log_transition(object.attributes) end end [Vehicle, Switch, Project].each do |klass| klass.state_machines.each do |attribute, machine| machine.before_transition StateMachineObserver.method(:before_transition) end end
Additional observer-like behavior may be exposed by the various integrations available. See below for more information on integrations.
Hooking in behavior to the generated instance / class methods from the state machine, events, and states is very simple because of the way these methods are generated on the class. Using the class‘s ancestors, the original generated method can be referred to via super. For example,
class Vehicle state_machine do event :park do ... end end def park(*args) logger.info "..." super end end
In the above example, the park instance method that‘s generated on the Vehicle class (by the associated event) is overridden with custom behavior. Once this behavior is complete, the original method from the state machine is invoked by simply calling super.
The same technique can be used for state, state_name, and all other instance and class methods on the Vehicle class.
By default state_machine does not redefine methods that exist on superclasses (including Object) or any modules (including Kernel) that were included before it was defined. This is in order to ensure that existing behavior on the class is not broken by the inclusion of state_machine.
If a conflicting method is detected, state_machine will generate a warning. For example, consider the following class:
class Vehicle state_machine do event :open do ... end end end
In the above class, an event named "open" is defined for its state machine. However, "open" is already defined as an instance method in Ruby‘s Kernel module that gets included in every Object. As a result, state_machine will generate the following warning:
Instance method "open" is already defined in Object, use generic helper instead or set StateMachine::Machine.ignore_method_conflicts = true.
Even though you may not be using Kernel‘s implementation of the "open" instance method, state_machine isn‘t aware of this and, as a result, stays safe and just skips redefining the method.
As with almost all helpers methods defined by state_machine in your class, there are generic methods available for working around this method conflict. In the example above, you can invoke the "open" event like so:
vehicle = Vehicle.new # => #<Vehicle:0xb72686b4 @state=nil> vehicle.fire_events(:open) # => true # This will not work vehicle.open # => NoMethodError: private method `open' called for #<Vehicle:0xb72686b4 @state=nil>
If you want to take on the risk of overriding existing methods and just ignore method conflicts altogether, you can do so by setting the following configuration:
StateMachine::Machine.ignore_method_conflicts = true
This will allow you to define events like "open" as described above and still generate the "open" instance helper method. For example:
StateMachine::Machine.ignore_method_conflicts = true class Vehicle state_machine do event :open do ... end end vehicle = Vehicle.new # => #<Vehicle:0xb72686b4 @state=nil> vehicle.open # => true
By default, state_machine helps prevent you from making mistakes and accidentally overriding methods that you didn‘t intend to. Once you understand this and what the consequences are, setting the ignore_method_conflicts option is a perfectly reasonable workaround.
By default, state machines are library-agnostic, meaning that they work on any Ruby class and have no external dependencies. However, there are certain libraries which expose additional behavior that can be taken advantage of by state machines.
This library is built to work out of the box with a few popular Ruby libraries that allow for additional behavior to provide a cleaner and smoother experience. This is especially the case for objects backed by a database that may allow for transactions, persistent storage, search/filters, callbacks, etc.
When a state machine is defined for classes using any of the above libraries, it will try to automatically determine the integration to use (Agnostic, ActiveModel, ActiveRecord, DataMapper, Mongoid, MongoMapper, or Sequel) based on the class definition. To see how each integration affects the machine‘s behavior, refer to all constants defined under the StateMachine::Integrations namespace.
action | [R] | The action to invoke when an object transitions |
callbacks | [R] |
The callbacks to invoke before/after a transition is performed
Maps :before => callbacks and :after => callbacks |
default_messages | [RW] | |
events | [R] | The events that trigger transitions. These are sorted, by default, in the order in which they were defined. |
ignore_method_conflicts | [RW] | |
name | [R] | The name of the machine, used for scoping methods generated for the machine as a whole (not states or events) |
namespace | [R] | An identifier that forces all methods (including state predicates and event methods) to be generated with the value prefixed or suffixed, depending on the context. |
owner_class | [RW] | The class that the machine is defined in |
states | [R] |
A list of all of the states known to this state machine. This will pull states from
the following sources:
These are sorted, by default, in the order in which they were referenced. |
use_transactions | [R] | Whether the machine will use transactions when firing events |
Draws the state machines defined in the given classes using GraphViz. The given classes must be a comma-delimited string of class names.
Configuration options:
# File lib/state_machine/machine.rb, line 464 464: def draw(class_names, options = {}) 465: raise ArgumentError, 'At least one class must be specified' unless class_names && class_names.split(',').any? 466: 467: # Load any files 468: if files = options.delete(:file) 469: files.split(',').each {|file| require file} 470: end 471: 472: class_names.split(',').each do |class_name| 473: # Navigate through the namespace structure to get to the class 474: klass = Object 475: class_name.split('::').each do |name| 476: klass = klass.const_defined?(name) ? klass.const_get(name) : klass.const_missing(name) 477: end 478: 479: # Draw each of the class's state machines 480: klass.state_machines.each_value do |machine| 481: machine.draw(options) 482: end 483: end 484: end
Attempts to find or create a state machine for the given class. For example,
StateMachine::Machine.find_or_create(Vehicle) StateMachine::Machine.find_or_create(Vehicle, :initial => :parked) StateMachine::Machine.find_or_create(Vehicle, :status) StateMachine::Machine.find_or_create(Vehicle, :status, :initial => :parked)
If a machine of the given name already exists in one of the class‘s superclasses, then a copy of that machine will be created and stored in the new owner class (the original will remain unchanged).
# File lib/state_machine/machine.rb, line 431 431: def find_or_create(owner_class, *args, &block) 432: options = args.last.is_a?(Hash) ? args.pop : {} 433: name = args.first || :state 434: 435: # Find an existing machine 436: if owner_class.respond_to?(:state_machines) && machine = owner_class.state_machines[name] 437: # Only create a new copy if changes are being made to the machine in 438: # a subclass 439: if machine.owner_class != owner_class && (options.any? || block_given?) 440: machine = machine.clone 441: machine.initial_state = options[:initial] if options.include?(:initial) 442: machine.owner_class = owner_class 443: end 444: 445: # Evaluate DSL 446: machine.instance_eval(&block) if block_given? 447: else 448: # No existing machine: create a new one 449: machine = new(owner_class, name, options, &block) 450: end 451: 452: machine 453: end
Creates a new state machine for the given attribute
# File lib/state_machine/machine.rb, line 539 539: def initialize(owner_class, *args, &block) 540: options = args.last.is_a?(Hash) ? args.pop : {} 541: assert_valid_keys(options, :attribute, :initial, :initialize, :action, :plural, :namespace, :integration, :messages, :use_transactions) 542: 543: # Find an integration that matches this machine's owner class 544: if options.include?(:integration) 545: @integration = StateMachine::Integrations.find_by_name(options[:integration]) if options[:integration] 546: else 547: @integration = StateMachine::Integrations.match(owner_class) 548: end 549: 550: if @integration 551: extend @integration 552: options = (@integration.defaults || {}).merge(options) 553: end 554: 555: # Add machine-wide defaults 556: options = {:use_transactions => true, :initialize => true}.merge(options) 557: 558: # Set machine configuration 559: @name = args.first || :state 560: @attribute = options[:attribute] || @name 561: @events = EventCollection.new(self) 562: @states = StateCollection.new(self) 563: @callbacks = {:before => [], :after => [], :failure => []} 564: @namespace = options[:namespace] 565: @messages = options[:messages] || {} 566: @action = options[:action] 567: @use_transactions = options[:use_transactions] 568: @initialize_state = options[:initialize] 569: self.owner_class = owner_class 570: self.initial_state = options[:initial] unless sibling_machines.any? 571: 572: # Merge with sibling machine configurations 573: add_sibling_machine_configs 574: 575: # Define class integration 576: define_helpers 577: define_scopes(options[:plural]) 578: after_initialize 579: 580: # Evaluate DSL 581: instance_eval(&block) if block_given? 582: end
Determines whether an action hook was defined for firing attribute-based event transitions when the configured action gets called.
# File lib/state_machine/machine.rb, line 1917 1917: def action_hook?(self_only = false) 1918: @action_hook_defined || !self_only && owner_class.state_machines.any? {|name, machine| machine.action == action && machine != self && machine.action_hook?(true)} 1919: end
Creates a callback that will be invoked after a transition failures to be performed so long as the given requirements match the transition.
See before_transition for a description of the possible configurations for defining callbacks. Note however that you cannot define the state requirements in these callbacks. You may only define event requirements.
Failure callbacks get invoked whenever an event fails to execute. This can happen when no transition is available, a before callback halts execution, or the action associated with this machine fails to succeed. In any of these cases, any failure callback that matches the attempted transition will be run.
For example,
class Vehicle state_machine do after_failure do |vehicle, transition| logger.error "vehicle #{vehicle} failed to transition on #{transition.event}" end after_failure :on => :ignite, :do => :log_ignition_failure ... end end
# File lib/state_machine/machine.rb, line 1730 1730: def after_failure(*args, &block) 1731: options = (args.last.is_a?(Hash) ? args.pop : {}) 1732: options[:do] = args if args.any? 1733: assert_valid_keys(options, :on, :do, :if, :unless) 1734: 1735: add_callback(:failure, options, &block) 1736: end
Creates a callback that will be invoked after a transition is performed so long as the given requirements match the transition.
See before_transition for a description of the possible configurations for defining callbacks.
# File lib/state_machine/machine.rb, line 1635 1635: def after_transition(*args, &block) 1636: options = (args.last.is_a?(Hash) ? args.pop : {}) 1637: options[:do] = args if args.any? 1638: add_callback(:after, options, &block) 1639: end
Creates a callback that will be invoked around a transition so long as the given requirements match the transition.
Around callbacks wrap transitions, executing code both before and after. These callbacks are defined in the exact same manner as before / after callbacks with the exception that the transition must be yielded to in order to finish running it.
If defining around callbacks using blocks, you must yield within the transition by directly calling the block (since yielding is not allowed within blocks).
For example,
class Vehicle state_machine do around_transition do |block| Benchmark.measure { block.call } end around_transition do |vehicle, block| logger.info "vehicle was #{state}..." block.call logger.info "...and is now #{state}" end around_transition do |vehicle, transition, block| logger.info "before #{transition.event}: #{vehicle.state}" block.call logger.info "after #{transition.event}: #{vehicle.state}" end end end
Notice that referencing the block is similar to doing so within an actual method definition in that it is always the last argument.
On the other hand, if you‘re defining around callbacks using method references, you can yield like normal:
class Vehicle state_machine do around_transition :benchmark ... end def benchmark Benchmark.measure { yield } end end
See before_transition for a description of the possible configurations for defining callbacks.
# File lib/state_machine/machine.rb, line 1696 1696: def around_transition(*args, &block) 1697: options = (args.last.is_a?(Hash) ? args.pop : {}) 1698: options[:do] = args if args.any? 1699: add_callback(:around, options, &block) 1700: end
Creates a callback that will be invoked before a transition is performed so long as the given requirements match the transition.
Callbacks must be defined as either an argument, in the :do option, or as a block. For example,
class Vehicle state_machine do before_transition :set_alarm before_transition :set_alarm, all => :parked before_transition all => :parked, :do => :set_alarm before_transition all => :parked do |vehicle, transition| vehicle.set_alarm end ... end end
Notice that the first three callbacks are the same in terms of how the methods to invoke are defined. However, using the :do can provide for a more fluid DSL.
In addition, multiple callbacks can be defined like so:
class Vehicle state_machine do before_transition :set_alarm, :lock_doors, all => :parked before_transition all => :parked, :do => [:set_alarm, :lock_doors] before_transition :set_alarm do |vehicle, transition| vehicle.lock_doors end end end
Notice that the different ways of configuring methods can be mixed.
Callbacks can require that the machine be transitioning from and to specific states. These requirements use a Hash syntax to map beginning states to ending states. For example,
before_transition :parked => :idling, :idling => :first_gear, :do => :set_alarm
In this case, the set_alarm callback will only be called if the machine is transitioning from parked to idling or from idling to parked.
To help define state requirements, a set of helpers are available for slightly more complex matching:
See StateMachine::MatcherHelpers for more information.
Examples:
before_transition :parked => [:idling, :first_gear], :do => ... # Matches from parked to idling or first_gear before_transition all - [:parked, :idling] => :idling, :do => ... # Matches from every state except parked and idling to idling before_transition all => :parked, :do => ... # Matches all states to parked before_transition any => same, :do => ... # Matches every loopback
In addition to state requirements, an event requirement can be defined so that the callback is only invoked on specific events using the on option. This can also use the same matcher helpers as the state requirements.
Examples:
before_transition :on => :ignite, :do => ... # Matches only on ignite before_transition :on => all - :ignite, :do => ... # Matches on every event except ignite before_transition :parked => :idling, :on => :ignite, :do => ... # Matches from parked to idling on ignite
Requirements can also be defined using verbose options rather than the implicit Hash syntax and helper methods described above.
Configuration options:
Examples:
before_transition :from => :ignite, :to => :idling, :on => :park, :do => ... before_transition :except_from => :ignite, :except_to => :idling, :except_on => :park, :do => ...
In addition to the state/event requirements, a condition can also be defined to help determine whether the callback should be invoked.
Configuration options:
Examples:
before_transition :parked => :idling, :if => :moving?, :do => ... before_transition :on => :ignite, :unless => :seatbelt_on?, :do => ...
In addition to passing the object being transitioned, the actual transition describing the context (e.g. event, from, to) can be accessed as well. This additional argument is only passed if the callback allows for it.
For example,
class Vehicle # Only specifies one parameter (the object being transitioned) before_transition all => :parked do |vehicle| vehicle.set_alarm end # Specifies 2 parameters (object being transitioned and actual transition) before_transition all => :parked do |vehicle, transition| vehicle.set_alarm(transition) end end
Note that the object in the callback will only be passed in as an argument if callbacks are configured to not be bound to the object involved. This is the default and may change on a per-integration basis.
See StateMachine::Transition for more information about the attributes available on the transition.
Below is an example of a class with one state machine and various types of before transitions defined for it:
class Vehicle state_machine do # Before all transitions before_transition :update_dashboard # Before specific transition: before_transition [:first_gear, :idling] => :parked, :on => :park, :do => :take_off_seatbelt # With conditional callback: before_transition all => :parked, :do => :take_off_seatbelt, :if => :seatbelt_on? # Using helpers: before_transition all - :stalled => same, :on => any - :crash, :do => :update_dashboard ... end end
As can be seen, any number of transitions can be created using various combinations of configuration options.
# File lib/state_machine/machine.rb, line 1624 1624: def before_transition(*args, &block) 1625: options = (args.last.is_a?(Hash) ? args.pop : {}) 1626: options[:do] = args if args.any? 1627: add_callback(:before, options, &block) 1628: end
Defines a new helper method in an instance or class scope with the given name. If the method is already defined in the scope, then this will not override it.
If passing in a block, there are two side effects to be aware of
Example:
# Instance helper machine.define_helper(:instance, :state_name) do |machine, object| machine.states.match(object).name end # Class helper machine.define_helper(:class, :state_machine_name) do |machine, klass| "State" end
You can also define helpers using string evaluation like so:
# Instance helper machine.define_helper :instance, <<-end_eval, __FILE__, __LINE__ + 1 def state_name self.class.state_machine(:state).states.match(self).name end end_eval # Class helper machine.define_helper :class, <<-end_eval, __FILE__, __LINE__ + 1 def state_machine_name "State" end end_eval
# File lib/state_machine/machine.rb, line 742 742: def define_helper(scope, method, *args, &block) 743: helper_module = @helper_modules.fetch(scope) 744: 745: if block_given? 746: if !self.class.ignore_method_conflicts && conflicting_ancestor = owner_class_ancestor_has_method?(scope, method) 747: ancestor_name = conflicting_ancestor.name && !conflicting_ancestor.name.empty? ? conflicting_ancestor.name : conflicting_ancestor.to_s 748: warn "#{scope == :class ? 'Class' : 'Instance'} method \"#{method}\" is already defined in #{ancestor_name}, use generic helper instead or set StateMachine::Machine.ignore_method_conflicts = true." 749: else 750: name = self.name 751: helper_module.class_eval do 752: define_method(method) do |*args| 753: block.call((scope == :instance ? self.class : self).state_machine(name), self, *args) 754: end 755: end 756: end 757: else 758: helper_module.class_eval(method, *args) 759: end 760: end
Draws a directed graph of the machine for visualizing the various events, states, and their transitions.
This requires both the Ruby graphviz gem and the graphviz library be installed on the system.
Configuration options:
# File lib/state_machine/machine.rb, line 1867 1867: def draw(options = {}) 1868: options = { 1869: :name => "#{owner_class.name}_#{name}", 1870: :path => '.', 1871: :format => 'png', 1872: :font => 'Arial', 1873: :orientation => 'portrait' 1874: }.merge(options) 1875: assert_valid_keys(options, :name, :path, :format, :font, :orientation) 1876: 1877: begin 1878: # Load the graphviz library 1879: require 'rubygems' 1880: gem 'ruby-graphviz', '>=0.9.0' 1881: require 'graphviz' 1882: 1883: graph = GraphViz.new('G', :rankdir => options[:orientation] == 'landscape' ? 'LR' : 'TB') 1884: 1885: # Add nodes 1886: states.by_priority.each do |state| 1887: node = state.draw(graph) 1888: node.fontname = options[:font] 1889: end 1890: 1891: # Add edges 1892: events.each do |event| 1893: edges = event.draw(graph) 1894: edges.each {|edge| edge.fontname = options[:font]} 1895: end 1896: 1897: # Generate the graph 1898: graphvizVersion = Constants::RGV_VERSION.split('.') 1899: file = File.join(options[:path], "#{options[:name]}.#{options[:format]}") 1900: 1901: if graphvizVersion[0] == '0' && graphvizVersion[1] == '9' && graphvizVersion[2] == '0' 1902: outputOptions = {:output => options[:format], :file => file} 1903: else 1904: outputOptions = {options[:format] => file} 1905: end 1906: 1907: graph.output(outputOptions) 1908: graph 1909: rescue LoadError => ex 1910: $stderr.puts "Cannot draw the machine (#{ex.message}). `gem install ruby-graphviz` >= v0.9.0 and try again." 1911: false 1912: end 1913: end
Gets a description of the errors for the given object. This is used to provide more detailed information when an InvalidTransition exception is raised.
# File lib/state_machine/machine.rb, line 1820 1820: def errors_for(object) 1821: '' 1822: end
Defines one or more events for the machine and the transitions that can be performed when those events are run.
This method is also aliased as on for improved compatibility with using a domain-specific language.
Configuration options:
The following instance methods are generated when a new event is defined (the "park" event is used as an example):
With a namespace of "car", the above names map to the following methods:
The can_park? and park_transition helpers both take an optional set of requirements for determining what transitions are available for the current object. These requirements include:
event requires a block which allows you to define the possible transitions that can happen as a result of that event. For example,
event :park, :stop do transition :idling => :parked end event :first_gear do transition :parked => :first_gear, :if => :seatbelt_on? transition :parked => same # Allow to loopback if seatbelt is off end
See StateMachine::Event#transition for more information on the possible options that can be passed in.
Note that this block is executed within the context of the actual event object. As a result, you will not be able to reference any class methods on the model without referencing the class itself. For example,
class Vehicle def self.safe_states [:parked, :idling, :stalled] end state_machine do event :park do transition Vehicle.safe_states => :parked end end end
By default, this will define an instance method (with the same name as the event) that will fire the next possible transition for that. Although the before_transition, after_transition, and around_transition hooks allow you to define behavior that gets executed as a result of the event‘s transition, you can also override the event method in order to have a little more fine-grained control.
For example:
class Vehicle state_machine do event :park do ... end end def park(*) take_deep_breath # Executes before the transition (and before_transition hooks) even if no transition is possible if result = super # Runs the transition and all before/after/around hooks applaud # Executes after the transition (and after_transition hooks) end result end end
There are a few important things to note here. First, the method signature is defined with an unlimited argument list in order to allow callers to continue passing arguments that are expected by state_machine. For example, it will still allow calls to park with a single parameter for skipping the configured action.
Second, the overridden event method must call super in order to run the logic for running the next possible transition. In order to remain consistent with other events, the result of super is returned.
Third, any behavior defined in this method will not get executed if you‘re taking advantage of attribute-based event transitions. For example:
vehicle = Vehicle.new vehicle.state_event = 'park' vehicle.save
In this case, the park event will run the before/after/around transition hooks and transition the state, but the behavior defined in the overriden park method will not be executed.
Additional arguments can be passed into events and accessed by transition hooks like so:
class Vehicle state_machine do after_transition :on => :park do |vehicle, transition| kind = *transition.args # :parallel ... end after_transition :on => :park, :do => :take_deep_breath event :park do ... end def take_deep_breath(transition) kind = *transition.args # :parallel ... end end end vehicle = Vehicle.new vehicle.park(:parallel)
Remember that if the last argument is a boolean, it will be used as the run_action parameter to the event action. Using the park action example from above, you can might call it like so:
vehicle.park # => Uses default args and runs machine action vehicle.park(:parallel) # => Specifies the +kind+ argument and runs the machine action vehicle.park(:parallel, false) # => Specifies the +kind+ argument and *skips* the machine action
If you decide to override the park event method and define additional arguments, you can do so as shown below:
class Vehicle state_machine do event :park do ... end end def park(kind = :parallel, *args) take_deep_breath if kind == :parallel super end end
Note that super is called instead of super(*args). This allow the entire arguments list to be accessed by transition callbacks through StateMachine::Transition#args.
The all / any matchers can be used to easily execute blocks for a group of events. Note, however, that you cannot use these matchers to set configurations for events. Blocks using these matchers can be defined at any point in the state machine and will always get applied to the proper events.
For example:
state_machine :initial => :parked do ... event all - [:crash] do transition :stalled => :parked end end
class Vehicle state_machine do # The park, stop, and halt events will all share the given transitions event :park, :stop, :halt do transition [:idling, :backing_up] => :parked end event :stop do transition :first_gear => :idling end event :ignite do transition :parked => :idling transition :idling => same # Allow ignite while still idling end end end
# File lib/state_machine/machine.rb, line 1326 1326: def event(*names, &block) 1327: options = names.last.is_a?(Hash) ? names.pop : {} 1328: assert_valid_keys(options, :human_name) 1329: 1330: # Store the context so that it can be used for / matched against any event 1331: # that gets added 1332: @events.context(names, &block) if block_given? 1333: 1334: if names.first.is_a?(Matcher) 1335: # Add any events referenced in the matcher. When matchers are used, 1336: # events are not allowed to be configured. 1337: raise ArgumentError, "Cannot configure events when using matchers (using #{options.inspect})" if options.any? 1338: events = add_events(names.first.values) 1339: else 1340: events = add_events(names) 1341: 1342: # Update the configuration for the event(s) 1343: events.each do |event| 1344: event.human_name = options[:human_name] if options.include?(:human_name) 1345: 1346: # Add any states that may have been referenced within the event 1347: add_states(event.known_states) 1348: end 1349: end 1350: 1351: events.length == 1 ? events.first : events 1352: end
Generates the message to use when invalidating the given object after failing to transition on a specific event
# File lib/state_machine/machine.rb, line 1832 1832: def generate_message(name, values = []) 1833: (@messages[name] || self.class.default_messages[name]) % values.map {|value| value.last} 1834: end
Gets the initial state of the machine for the given object. If a dynamic initial state was configured for this machine, then the object will be passed into the lambda block to help determine the actual state.
With a static initial state:
class Vehicle state_machine :initial => :parked do ... end end vehicle = Vehicle.new Vehicle.state_machine.initial_state(vehicle) # => #<StateMachine::State name=:parked value="parked" initial=true>
With a dynamic initial state:
class Vehicle attr_accessor :force_idle state_machine :initial => lambda {|vehicle| vehicle.force_idle ? :idling : :parked} do ... end end vehicle = Vehicle.new vehicle.force_idle = true Vehicle.state_machine.initial_state(vehicle) # => #<StateMachine::State name=:idling value="idling" initial=false> vehicle.force_idle = false Vehicle.state_machine.initial_state(vehicle) # => #<StateMachine::State name=:parked value="parked" initial=false>
# File lib/state_machine/machine.rb, line 670 670: def initial_state(object) 671: states.fetch(dynamic_initial_state? ? evaluate_method(object, @initial_state) : @initial_state) if instance_variable_defined?('@initial_state') 672: end
Sets the initial state of the machine. This can be either the static name of a state or a lambda block which determines the initial state at creation time.
# File lib/state_machine/machine.rb, line 628 628: def initial_state=(new_initial_state) 629: @initial_state = new_initial_state 630: add_states([@initial_state]) unless dynamic_initial_state? 631: 632: # Update all states to reflect the new initial state 633: states.each {|state| state.initial = (state.name == @initial_state)} 634: end
Initializes the state on the given object. Initial values are only set if the machine‘s attribute hasn‘t been previously initialized.
Configuration options:
# File lib/state_machine/machine.rb, line 687 687: def initialize_state(object, options = {}) 688: state = initial_state(object) 689: if state && (options[:force] || initialize_state?(object)) 690: value = state.value 691: 692: if hash = options[:to] 693: hash[attribute.to_s] = value 694: else 695: write(object, :state, value) 696: end 697: end 698: end
Marks the given object as invalid with the given message.
By default, this is a no-op.
# File lib/state_machine/machine.rb, line 1814 1814: def invalidate(object, attribute, message, values = []) 1815: end
Sets the class which is the owner of this state machine. Any methods generated by states, events, or other parts of the machine will be defined on the given owner class.
# File lib/state_machine/machine.rb, line 600 600: def owner_class=(klass) 601: @owner_class = klass 602: 603: # Create modules for extending the class with state/event-specific methods 604: @helper_modules = helper_modules = {:instance => HelperModule.new(self, :instance), :class => HelperModule.new(self, :class)} 605: owner_class.class_eval do 606: extend helper_modules[:class] 607: include helper_modules[:instance] 608: end 609: 610: # Add class-/instance-level methods to the owner class for state initialization 611: unless owner_class < StateMachine::InstanceMethods 612: owner_class.class_eval do 613: extend StateMachine::ClassMethods 614: include StateMachine::InstanceMethods 615: end 616: 617: define_state_initializer if @initialize_state 618: end 619: 620: # Record this machine as matched to the name in the current owner class. 621: # This will override any machines mapped to the same name in any superclasses. 622: owner_class.state_machines[name] = self 623: end
Generates a list of the possible transition sequences that can be run on the given object. These paths can reveal all of the possible states and events that can be encountered in the object‘s state machine based on the object‘s current state.
Configuration options:
Note that the object is never modified when the list of paths is generated.
class Vehicle state_machine :initial => :parked do event :ignite do transition :parked => :idling end event :shift_up do transition :idling => :first_gear, :first_gear => :second_gear end event :shift_down do transition :second_gear => :first_gear, :first_gear => :idling end end end vehicle = Vehicle.new # => #<Vehicle:0xb7c27024 @state="parked"> vehicle.state # => "parked" vehicle.state_paths # => [ # [#<StateMachine::Transition attribute=:state event=:ignite from="parked" from_name=:parked to="idling" to_name=:idling>, # #<StateMachine::Transition attribute=:state event=:shift_up from="idling" from_name=:idling to="first_gear" to_name=:first_gear>, # #<StateMachine::Transition attribute=:state event=:shift_up from="first_gear" from_name=:first_gear to="second_gear" to_name=:second_gear>, # #<StateMachine::Transition attribute=:state event=:shift_down from="second_gear" from_name=:second_gear to="first_gear" to_name=:first_gear>, # #<StateMachine::Transition attribute=:state event=:shift_down from="first_gear" from_name=:first_gear to="idling" to_name=:idling>], # # [#<StateMachine::Transition attribute=:state event=:ignite from="parked" from_name=:parked to="idling" to_name=:idling>, # #<StateMachine::Transition attribute=:state event=:shift_up from="idling" from_name=:idling to="first_gear" to_name=:first_gear>, # #<StateMachine::Transition attribute=:state event=:shift_down from="first_gear" from_name=:first_gear to="idling" to_name=:idling>] # ] vehicle.state_paths(:from => :parked, :to => :second_gear) # => [ # [#<StateMachine::Transition attribute=:state event=:ignite from="parked" from_name=:parked to="idling" to_name=:idling>, # #<StateMachine::Transition attribute=:state event=:shift_up from="idling" from_name=:idling to="first_gear" to_name=:first_gear>, # #<StateMachine::Transition attribute=:state event=:shift_up from="first_gear" from_name=:first_gear to="second_gear" to_name=:second_gear>] # ]
In addition to getting the possible paths that can be accessed, you can also get summary information about the states / events that can be accessed at some point along one of the paths. For example:
# Get the list of states that can be accessed from the current state vehicle.state_paths.to_states # => [:idling, :first_gear, :second_gear] # Get the list of events that can be accessed from the current state vehicle.state_paths.events # => [:ignite, :shift_up, :shift_down]
# File lib/state_machine/machine.rb, line 1807 1807: def paths_for(object, requirements = {}) 1808: PathCollection.new(object, self, requirements) 1809: end
Gets the current value stored in the given object‘s attribute.
For example,
class Vehicle state_machine :initial => :parked do ... end end vehicle = Vehicle.new # => #<Vehicle:0xb7d94ab0 @state="parked"> Vehicle.state_machine.read(vehicle, :state) # => "parked" # Equivalent to vehicle.state Vehicle.state_machine.read(vehicle, :event) # => nil # Equivalent to vehicle.state_event
# File lib/state_machine/machine.rb, line 1075 1075: def read(object, attribute, ivar = false) 1076: attribute = self.attribute(attribute) 1077: ivar ? object.instance_variable_get("@#{attribute}") : object.send(attribute) 1078: end
Resets any errors previously added when invalidating the given object.
By default, this is a no-op.
# File lib/state_machine/machine.rb, line 1827 1827: def reset(object) 1828: end
Customizes the definition of one or more states in the machine.
Configuration options:
Whenever a state is automatically discovered in the state machine, its default value is assumed to be the stringified version of the name. For example,
class Vehicle state_machine :initial => :parked do event :ignite do transition :parked => :idling end end end
In the above state machine, there are two states automatically discovered: :parked and :idling. These states, by default, will store their stringified equivalents when an object moves into that state (e.g. "parked" / "idling").
For legacy systems or when tying state machines into existing frameworks, it‘s oftentimes necessary to need to store a different value for a state than the default. In order to continue taking advantage of an expressive state machine and helper methods, every defined state can be re-configured with a custom stored value. For example,
class Vehicle state_machine :initial => :parked do event :ignite do transition :parked => :idling end state :idling, :value => 'IDLING' state :parked, :value => 'PARKED end end
This is also useful if being used in association with a database and, instead of storing the state name in a column, you want to store the state‘s foreign key:
class VehicleState < ActiveRecord::Base end class Vehicle < ActiveRecord::Base state_machine :attribute => :state_id, :initial => :parked do event :ignite do transition :parked => :idling end states.each do |state| self.state(state.name, :value => lambda { VehicleState.find_by_name(state.name.to_s).id }, :cache => true) end end end
In the above example, each known state is configured to store it‘s associated database id in the state_id attribute. Also, notice that a lambda block is used to define the state‘s value. This is required in situations (like testing) where the model is loaded without any existing data (i.e. no VehicleState records available).
One caveat to the above example is to keep performance in mind. To avoid constant db hits for looking up the VehicleState ids, the value is cached by specifying the :cache option. Alternatively, a custom caching strategy can be used like so:
class VehicleState < ActiveRecord::Base cattr_accessor :cache_store self.cache_store = ActiveSupport::Cache::MemoryStore.new def self.find_by_name(name) cache_store.fetch(name) { find(:first, :conditions => {:name => name}) } end end
In addition to customizing states with other value types, lambda blocks can also be specified to allow for a state‘s value to be determined dynamically at runtime. For example,
class Vehicle state_machine :purchased_at, :initial => :available do event :purchase do transition all => :purchased end event :restock do transition all => :available end state :available, :value => nil state :purchased, :if => lambda {|value| !value.nil?}, :value => lambda {Time.now} end end
In the above definition, the :purchased state is customized with both a dynamic value and a value matcher.
When an object transitions to the purchased state, the value‘s lambda block will be called. This will get the current time and store it in the object‘s purchased_at attribute.
Note that the custom matcher is very important here. Since there‘s no way for the state machine to figure out an object‘s state when it‘s set to a runtime value, it must be explicitly defined. If the :if option were not configured for the state, then an ArgumentError exception would be raised at runtime, indicating that the state machine could not figure out what the current state of the object was.
Behaviors define a series of methods to mixin with objects when the current state matches the given one(s). This allows instance methods to behave a specific way depending on what the value of the object‘s state is.
For example,
class Vehicle attr_accessor :driver attr_accessor :passenger state_machine :initial => :parked do event :ignite do transition :parked => :idling end state :parked do def speed 0 end def rotate_driver driver = self.driver self.driver = passenger self.passenger = driver true end end state :idling, :first_gear do def speed 20 end def rotate_driver self.state = 'parked' rotate_driver end end other_states :backing_up end end
In the above example, there are two dynamic behaviors defined for the class:
Each of these behaviors are instance methods on the Vehicle class. However, which method actually gets invoked is based on the current state of the object. Using the above class as the example:
vehicle = Vehicle.new vehicle.driver = 'John' vehicle.passenger = 'Jane' # Behaviors in the "parked" state vehicle.state # => "parked" vehicle.speed # => 0 vehicle.rotate_driver # => true vehicle.driver # => "Jane" vehicle.passenger # => "John" vehicle.ignite # => true # Behaviors in the "idling" state vehicle.state # => "idling" vehicle.speed # => 20 vehicle.rotate_driver # => true vehicle.driver # => "John" vehicle.passenger # => "Jane"
As can be seen, both the speed and rotate_driver instance method implementations changed how they behave based on what the current state of the vehicle was.
If a specific behavior has not been defined for a state, then a NoMethodError exception will be raised, indicating that that method would not normally exist for an object with that state.
Using the example from before:
vehicle = Vehicle.new vehicle.state = 'backing_up' vehicle.speed # => NoMethodError: undefined method 'speed' for #<Vehicle:0xb7d296ac> in state "backing_up"
The all / any matchers can be used to easily define behaviors for a group of states. Note, however, that you cannot use these matchers to set configurations for states. Behaviors using these matchers can be defined at any point in the state machine and will always get applied to the proper states.
For example:
state_machine :initial => :parked do ... state all - [:parked, :idling, :stalled] do validates_presence_of :speed def speed gear * 10 end end end
In addition to defining scopes for instance methods that are state-aware, the same can be done for certain types of class methods.
Some libraries have support for class-level methods that only run certain behaviors based on a conditions hash passed in. For example:
class Vehicle < ActiveRecord::Base state_machine do ... state :first_gear, :second_gear, :third_gear do validates_presence_of :speed validates_inclusion_of :speed, :in => 0..25, :if => :in_school_zone? end end end
In the above ActiveRecord model, two validations have been defined which will only run when the Vehicle object is in one of the three states: first_gear, second_gear, or +third_gear. Notice, also, that if/unless conditions can continue to be used.
This functionality is not library-specific and can work for any class-level method that is defined like so:
def validates_presence_of(attribute, options = {}) ... end
The minimum requirement is that the last argument in the method be an options hash which contains at least :if condition support.
# File lib/state_machine/machine.rb, line 1029 1029: def state(*names, &block) 1030: options = names.last.is_a?(Hash) ? names.pop : {} 1031: assert_valid_keys(options, :value, :cache, :if, :human_name) 1032: 1033: # Store the context so that it can be used for / matched against any state 1034: # that gets added 1035: @states.context(names, &block) if block_given? 1036: 1037: if names.first.is_a?(Matcher) 1038: # Add any states referenced in the matcher. When matchers are used, 1039: # states are not allowed to be configured. 1040: raise ArgumentError, "Cannot configure states when using matchers (using #{options.inspect})" if options.any? 1041: states = add_states(names.first.values) 1042: else 1043: states = add_states(names) 1044: 1045: # Update the configuration for the state(s) 1046: states.each do |state| 1047: if options.include?(:value) 1048: state.value = options[:value] 1049: self.states.update(state) 1050: end 1051: 1052: state.human_name = options[:human_name] if options.include?(:human_name) 1053: state.cache = options[:cache] if options.include?(:cache) 1054: state.matcher = options[:if] if options.include?(:if) 1055: end 1056: end 1057: 1058: states.length == 1 ? states.first : states 1059: end
Creates a new transition that determines what to change the current state to when an event fires.
The options for a new transition uses the Hash syntax to map beginning states to ending states. For example,
transition :parked => :idling, :idling => :first_gear, :on => :ignite
In this case, when the ignite event is fired, this transition will cause the state to be idling if it‘s current state is parked or first_gear if it‘s current state is idling.
To help define these implicit transitions, a set of helpers are available for slightly more complex matching:
See StateMachine::MatcherHelpers for more information.
Examples:
transition all => nil, :on => :ignite # Transitions to nil regardless of the current state transition all => :idling, :on => :ignite # Transitions to :idling regardless of the current state transition all - [:idling, :first_gear] => :idling, :on => :ignite # Transitions every state but :idling and :first_gear to :idling transition nil => :idling, :on => :ignite # Transitions to :idling from the nil state transition :parked => :idling, :on => :ignite # Transitions to :idling if :parked transition [:parked, :stalled] => :idling, :on => :ignite # Transitions to :idling if :parked or :stalled transition :parked => same, :on => :park # Loops :parked back to :parked transition [:parked, :stalled] => same, :on => [:park, :stall] # Loops either :parked or :stalled back to the same state on the park and stall events transition all - :parked => same, :on => :noop # Loops every state but :parked back to the same state # Transitions to :idling if :parked, :first_gear if :idling, or :second_gear if :first_gear transition :parked => :idling, :idling => :first_gear, :first_gear => :second_gear, :on => :shift_up
Transitions can also be defined use an explicit set of configuration options:
These options must be used when defining transitions within the context of a state.
Examples:
transition :to => nil, :on => :park transition :to => :idling, :on => :ignite transition :except_from => [:idling, :first_gear], :to => :idling, :on => :ignite transition :from => nil, :to => :idling, :on => :ignite transition :from => [:parked, :stalled], :to => :idling, :on => :ignite
In addition to the state requirements for each transition, a condition can also be defined to help determine whether that transition is available. These options will work on both the normal and verbose syntax.
Configuration options:
Examples:
transition :parked => :idling, :on => :ignite, :if => :moving? transition :parked => :idling, :on => :ignite, :unless => :stopped? transition :idling => :first_gear, :first_gear => :second_gear, :on => :shift_up, :if => :seatbelt_on? transition :from => :parked, :to => :idling, :on => ignite, :if => :moving? transition :from => :parked, :to => :idling, :on => ignite, :unless => :stopped?
Transitions are evaluated in the order in which they‘re defined. As a result, if more than one transition applies to a given object, then the first transition that matches will be performed.
# File lib/state_machine/machine.rb, line 1444 1444: def transition(options) 1445: raise ArgumentError, 'Must specify :on event' unless options[:on] 1446: 1447: branches = [] 1448: event(*Array(options.delete(:on))) { branches << transition(options) } 1449: 1450: branches.length == 1 ? branches.first : branches 1451: end
Runs a transaction, rolling back any changes if the yielded block fails.
This is only applicable to integrations that involve databases. By default, this will not run any transactions since the changes aren‘t taking place within the context of a database.
# File lib/state_machine/machine.rb, line 1841 1841: def within_transaction(object) 1842: if use_transactions 1843: transaction(object) { yield } 1844: else 1845: yield 1846: end 1847: end
Sets a new value in the given object‘s attribute.
For example,
class Vehicle state_machine :initial => :parked do ... end end vehicle = Vehicle.new # => #<Vehicle:0xb7d94ab0 @state="parked"> Vehicle.state_machine.write(vehicle, :state, 'idling') # => Equivalent to vehicle.state = 'idling' Vehicle.state_machine.write(vehicle, :event, 'park') # => Equivalent to vehicle.state_event = 'park' vehicle.state # => "idling" vehicle.event # => "park"
# File lib/state_machine/machine.rb, line 1095 1095: def write(object, attribute, value, ivar = false) 1096: attribute = self.attribute(attribute) 1097: ivar ? object.instance_variable_set("@#{attribute}", value) : object.send("#{attribute}=", value) 1098: end
The method to hook into for triggering transitions when invoked. By default, this is the action configured for the machine.
Since the default hook technique relies on module inheritance, the action must be defined in an ancestor of the owner classs in order for it to be the action hook.
# File lib/state_machine/machine.rb, line 2084 2084: def action_hook 2085: action && owner_class_ancestor_has_method?(:instance, action) ? action : nil 2086: end
Adds a new transition callback of the given type.
# File lib/state_machine/machine.rb, line 2211 2211: def add_callback(type, options, &block) 2212: callbacks[type == :around ? :before : type] << callback = Callback.new(type, options, &block) 2213: add_states(callback.known_states) 2214: callback 2215: end
Tracks the given set of events in the list of all known events for this machine
# File lib/state_machine/machine.rb, line 2234 2234: def add_events(new_events) 2235: new_events.map do |new_event| 2236: unless event = events[new_event] 2237: events << event = Event.new(self, new_event) 2238: end 2239: 2240: event 2241: end 2242: end
Updates this machine based on the configuration of other machines in the owner class that share the same target attribute.
# File lib/state_machine/machine.rb, line 2203 2203: def add_sibling_machine_configs 2204: # Add existing states 2205: sibling_machines.each do |machine| 2206: machine.states.each {|state| states << state unless states[state.name]} 2207: end 2208: end
Tracks the given set of states in the list of all known states for this machine
# File lib/state_machine/machine.rb, line 2219 2219: def add_states(new_states) 2220: new_states.map do |new_state| 2221: unless state = states[new_state] 2222: states << state = State.new(self, new_state) 2223: 2224: # Copy states over to sibling machines 2225: sibling_machines.each {|machine| machine.states << state} 2226: end 2227: 2228: state 2229: end 2230: end
Runs additional initialization hooks. By default, this is a no-op.
# File lib/state_machine/machine.rb, line 1923 1923: def after_initialize 1924: end
Adds helper methods for automatically firing events when an action is invoked
# File lib/state_machine/machine.rb, line 2052 2052: def define_action_helpers 2053: if action_hook 2054: @action_hook_defined = true 2055: define_action_hook 2056: end 2057: end
Determines whether action helpers should be defined for this machine. This is only true if there is an action configured and no other machines have process this same configuration already.
# File lib/state_machine/machine.rb, line 2046 2046: def define_action_helpers? 2047: action && !owner_class.state_machines.any? {|name, machine| machine.action == action && machine != self} 2048: end
Hooks directly into actions by defining the same method in an included module. As a result, when the action gets invoked, any state events defined for the object will get run. Method visibility is preserved.
# File lib/state_machine/machine.rb, line 2062 2062: def define_action_hook 2063: action_hook = self.action_hook 2064: action = self.action 2065: private_action_hook = owner_class.private_method_defined?(action_hook) 2066: 2067: # Only define helper if it hasn't 2068: define_helper :instance, "def \#{action_hook}(*)\nself.class.state_machines.transitions(self, \#{action.inspect}).perform { super }\nend\n\nprivate \#{action_hook.inspect} if \#{private_action_hook}\n", __FILE__, __LINE__ + 1 2069: end
Adds helper methods for getting information about this state machine‘s events
# File lib/state_machine/machine.rb, line 1993 1993: def define_event_helpers 1994: # Gets the events that are allowed to fire on the current object 1995: define_helper(:instance, attribute(:events)) do |machine, object, *args| 1996: machine.events.valid_for(object, *args).map {|event| event.name} 1997: end 1998: 1999: # Gets the next possible transitions that can be run on the current 2000: # object 2001: define_helper(:instance, attribute(:transitions)) do |machine, object, *args| 2002: machine.events.transitions_for(object, *args) 2003: end 2004: 2005: # Fire an arbitrary event for this machine 2006: define_helper(:instance, "fire_#{attribute(:event)}") do |machine, object, event, *args| 2007: machine.events.fetch(event).fire(object, *args) 2008: end 2009: 2010: # Add helpers for tracking the event / transition to invoke when the 2011: # action is called 2012: if action 2013: event_attribute = attribute(:event) 2014: define_helper(:instance, event_attribute) do |machine, object| 2015: # Interpret non-blank events as present 2016: event = machine.read(object, :event, true) 2017: event && !(event.respond_to?(:empty?) && event.empty?) ? event.to_sym : nil 2018: end 2019: 2020: # A roundabout way of writing the attribute is used here so that 2021: # integrations can hook into this modification 2022: define_helper(:instance, "#{event_attribute}=") do |machine, object, value| 2023: machine.write(object, :event, value, true) 2024: end 2025: 2026: event_transition_attribute = attribute(:event_transition) 2027: define_helper :instance, "protected; attr_accessor \#{event_transition_attribute.inspect}\n", __FILE__, __LINE__ + 1 2028: end 2029: end
Adds helper methods for interacting with the state machine, including for states, events, and transitions
# File lib/state_machine/machine.rb, line 1950 1950: def define_helpers 1951: define_state_accessor 1952: define_state_predicate 1953: define_event_helpers 1954: define_path_helpers 1955: define_action_helpers if define_action_helpers? 1956: define_name_helpers 1957: end
Adds helper methods for accessing naming information about states and events on the owner class
# File lib/state_machine/machine.rb, line 2119 2119: def define_name_helpers 2120: # Gets the humanized version of a state 2121: define_helper(:class, "human_#{attribute(:name)}") do |machine, klass, state| 2122: machine.states.fetch(state).human_name(klass) 2123: end 2124: 2125: # Gets the humanized version of an event 2126: define_helper(:class, "human_#{attribute(:event_name)}") do |machine, klass, event| 2127: machine.events.fetch(event).human_name(klass) 2128: end 2129: 2130: # Gets the state name for the current value 2131: define_helper(:instance, attribute(:name)) do |machine, object| 2132: machine.states.match!(object).name 2133: end 2134: 2135: # Gets the human state name for the current value 2136: define_helper(:instance, "human_#{attribute(:name)}") do |machine, object| 2137: machine.states.match!(object).human_name(object.class) 2138: end 2139: end
Adds helper methods for getting information about this state machine‘s available transition paths
# File lib/state_machine/machine.rb, line 2036 2036: def define_path_helpers 2037: # Gets the paths of transitions available to the current object 2038: define_helper(:instance, attribute(:paths)) do |machine, object, *args| 2039: machine.paths_for(object, *args) 2040: end 2041: end
Defines the with/without scope helpers for this attribute. Both the singular and plural versions of the attribute are defined for each scope helper. A custom plural can be specified if it cannot be automatically determined by either calling pluralize on the attribute name or adding an "s" to the end of the name.
# File lib/state_machine/machine.rb, line 2146 2146: def define_scopes(custom_plural = nil) 2147: plural = custom_plural || pluralize(name) 2148: 2149: [name, plural].uniq.each do |name| 2150: [:with, :without].each do |kind| 2151: method = "#{kind}_#{name}" 2152: 2153: if scope = send("create_#{kind}_scope", method) 2154: # Converts state names to their corresponding values so that they 2155: # can be looked up properly 2156: define_helper(:class, method) do |machine, klass, *states| 2157: run_scope(scope, machine, klass, states) 2158: end 2159: end 2160: end 2161: end 2162: end
Adds reader/writer methods for accessing the state attribute
# File lib/state_machine/machine.rb, line 1972 1972: def define_state_accessor 1973: attribute = self.attribute 1974: 1975: @helper_modules[:instance].class_eval { attr_reader attribute } unless owner_class_ancestor_has_method?(:instance, attribute) 1976: @helper_modules[:instance].class_eval { attr_writer attribute } unless owner_class_ancestor_has_method?(:instance, "#{attribute}=") 1977: end
Defines the initial values for state machine attributes. Static values are set prior to the original initialize method and dynamic values are set after the initialize method in case it is dependent on it.
# File lib/state_machine/machine.rb, line 1962 1962: def define_state_initializer 1963: define_helper :instance, "def initialize(*)\nself.class.state_machines.initialize_states(self) { super }\nend\n", __FILE__, __LINE__ + 1 1964: end
Adds predicate method to the owner class for determining the name of the current state
# File lib/state_machine/machine.rb, line 1981 1981: def define_state_predicate 1982: call_super = !!owner_class_ancestor_has_method?(:instance, "#{name}?") 1983: define_helper :instance, "def \#{name}?(*args)\nargs.empty? && (\#{call_super} || defined?(super)) ? super : self.class.state_machine(\#{name.inspect}).states.matches?(self, *args)\nend\n", __FILE__, __LINE__ + 1 1984: end
Determines if the machine‘s attribute needs to be initialized. This will only be true if the machine‘s attribute is blank.
# File lib/state_machine/machine.rb, line 1943 1943: def initialize_state?(object) 1944: value = read(object, :state) 1945: (value.nil? || value.respond_to?(:empty?) && value.empty?) && !states[value, :value] 1946: end
Determines whether there‘s already a helper method defined within the given scope. This is true only if one of the owner‘s ancestors defines the method and is further along in the ancestor chain than this machine‘s helper module.
# File lib/state_machine/machine.rb, line 2092 2092: def owner_class_ancestor_has_method?(scope, method) 2093: superclasses = owner_class.ancestors[1..-1].select {|ancestor| ancestor.is_a?(Class)} 2094: 2095: if scope == :class 2096: # Use singleton classes 2097: current = (class << owner_class; self; end) 2098: superclass = superclasses.first 2099: else 2100: current = owner_class 2101: superclass = owner_class.superclass 2102: end 2103: 2104: # Generate the list of modules that *only* occur in the owner class, but 2105: # were included *prior* to the helper modules, in addition to the 2106: # superclasses 2107: ancestors = current.ancestors - superclass.ancestors + superclasses 2108: ancestors = ancestors[ancestors.index(@helper_modules[scope])..-1].reverse 2109: 2110: # Search for for the first ancestor that defined this method 2111: ancestors.detect do |ancestor| 2112: ancestor = (class << ancestor; self; end) if scope == :class && ancestor.is_a?(Class) 2113: ancestor.method_defined?(method) || ancestor.private_method_defined?(method) 2114: end 2115: end
Pluralizes the given word using pluralize (if available) or simply adding an "s" to the end of the word
# File lib/state_machine/machine.rb, line 2173 2173: def pluralize(word) 2174: word = word.to_s 2175: if word.respond_to?(:pluralize) 2176: word.pluralize 2177: else 2178: "#{name}s" 2179: end 2180: end
Generates the results for the given scope based on one or more states to filter by
# File lib/state_machine/machine.rb, line 2166 2166: def run_scope(scope, machine, klass, states) 2167: values = states.flatten.map {|state| machine.states.fetch(state).value} 2168: scope.call(klass, values) 2169: end
Looks up other machines that have been defined in the owner class and are targeting the same attribute as this machine. When accessing sibling machines, they will be automatically copied for the current class if they haven‘t been already. This ensures that any configuration changes made to the sibling machines only affect this class and not any base class that may have originally defined the machine.
# File lib/state_machine/machine.rb, line 1932 1932: def sibling_machines 1933: owner_class.state_machines.inject([]) do |machines, (name, machine)| 1934: if machine.attribute == attribute && machine != self 1935: machines << (owner_class.state_machine(name) {}) 1936: end 1937: machines 1938: end 1939: end