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 either:
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.
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 415 415: def draw(class_names, options = {}) 416: raise ArgumentError, 'At least one class must be specified' unless class_names && class_names.split(',').any? 417: 418: # Load any files 419: if files = options.delete(:file) 420: files.split(',').each {|file| require file} 421: end 422: 423: class_names.split(',').each do |class_name| 424: # Navigate through the namespace structure to get to the class 425: klass = Object 426: class_name.split('::').each do |name| 427: klass = klass.const_defined?(name) ? klass.const_get(name) : klass.const_missing(name) 428: end 429: 430: # Draw each of the class's state machines 431: klass.state_machines.each_value do |machine| 432: machine.draw(options) 433: end 434: end 435: 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 382 382: def find_or_create(owner_class, *args, &block) 383: options = args.last.is_a?(Hash) ? args.pop : {} 384: name = args.first || :state 385: 386: # Find an existing machine 387: if owner_class.respond_to?(:state_machines) && machine = owner_class.state_machines[name] 388: # Only create a new copy if changes are being made to the machine in 389: # a subclass 390: if machine.owner_class != owner_class && (options.any? || block_given?) 391: machine = machine.clone 392: machine.initial_state = options[:initial] if options.include?(:initial) 393: machine.owner_class = owner_class 394: end 395: 396: # Evaluate DSL 397: machine.instance_eval(&block) if block_given? 398: else 399: # No existing machine: create a new one 400: machine = new(owner_class, name, options, &block) 401: end 402: 403: machine 404: end
Creates a new state machine for the given attribute
# File lib/state_machine/machine.rb, line 490 490: def initialize(owner_class, *args, &block) 491: options = args.last.is_a?(Hash) ? args.pop : {} 492: assert_valid_keys(options, :attribute, :initial, :initialize, :action, :plural, :namespace, :integration, :messages, :use_transactions) 493: 494: # Find an integration that matches this machine's owner class 495: if options.include?(:integration) 496: @integration = StateMachine::Integrations.find_by_name(options[:integration]) if options[:integration] 497: else 498: @integration = StateMachine::Integrations.match(owner_class) 499: end 500: 501: if @integration 502: extend @integration 503: options = (@integration.defaults || {}).merge(options) 504: end 505: 506: # Add machine-wide defaults 507: options = {:use_transactions => true, :initialize => true}.merge(options) 508: 509: # Set machine configuration 510: @name = args.first || :state 511: @attribute = options[:attribute] || @name 512: @events = EventCollection.new(self) 513: @states = StateCollection.new(self) 514: @callbacks = {:before => [], :after => [], :failure => []} 515: @namespace = options[:namespace] 516: @messages = options[:messages] || {} 517: @action = options[:action] 518: @use_transactions = options[:use_transactions] 519: @initialize_state = options[:initialize] 520: self.owner_class = owner_class 521: self.initial_state = options[:initial] unless sibling_machines.any? 522: 523: # Merge with sibling machine configurations 524: add_sibling_machine_configs 525: 526: # Define class integration 527: define_helpers 528: define_scopes(options[:plural]) 529: after_initialize 530: 531: # Evaluate DSL 532: instance_eval(&block) if block_given? 533: 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 1796 1796: def action_hook?(self_only = false) 1797: @action_hook_defined || !self_only && owner_class.state_machines.any? {|name, machine| machine.action == action && machine != self && machine.action_hook?(true)} 1798: 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 1616 1616: def after_failure(*args, &block) 1617: options = (args.last.is_a?(Hash) ? args.pop : {}) 1618: options[:do] = args if args.any? 1619: assert_valid_keys(options, :on, :do, :if, :unless) 1620: 1621: add_callback(:failure, options, &block) 1622: 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 1521 1521: def after_transition(*args, &block) 1522: options = (args.last.is_a?(Hash) ? args.pop : {}) 1523: options[:do] = args if args.any? 1524: add_callback(:after, options, &block) 1525: 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 1582 1582: def around_transition(*args, &block) 1583: options = (args.last.is_a?(Hash) ? args.pop : {}) 1584: options[:do] = args if args.any? 1585: add_callback(:around, options, &block) 1586: 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 1510 1510: def before_transition(*args, &block) 1511: options = (args.last.is_a?(Hash) ? args.pop : {}) 1512: options[:do] = args if args.any? 1513: add_callback(:before, options, &block) 1514: 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 693 693: def define_helper(scope, method, *args, &block) 694: helper_module = @helper_modules.fetch(scope) 695: 696: if block_given? 697: if !self.class.ignore_method_conflicts && conflicting_ancestor = owner_class_ancestor_has_method?(scope, method) 698: ancestor_name = conflicting_ancestor.name && !conflicting_ancestor.name.empty? ? conflicting_ancestor.name : conflicting_ancestor.to_s 699: warn "#{scope == :class ? 'Class' : 'Instance'} method \"#{method}\" is already defined in #{ancestor_name}, use generic helper instead." 700: else 701: name = self.name 702: helper_module.class_eval do 703: define_method(method) do |*args| 704: block.call((scope == :instance ? self.class : self).state_machine(name), self, *args) 705: end 706: end 707: end 708: else 709: helper_module.class_eval(method, *args) 710: end 711: 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 1746 1746: def draw(options = {}) 1747: options = { 1748: :name => "#{owner_class.name}_#{name}", 1749: :path => '.', 1750: :format => 'png', 1751: :font => 'Arial', 1752: :orientation => 'portrait' 1753: }.merge(options) 1754: assert_valid_keys(options, :name, :path, :format, :font, :orientation) 1755: 1756: begin 1757: # Load the graphviz library 1758: require 'rubygems' 1759: gem 'ruby-graphviz', '>=0.9.0' 1760: require 'graphviz' 1761: 1762: graph = GraphViz.new('G', :rankdir => options[:orientation] == 'landscape' ? 'LR' : 'TB') 1763: 1764: # Add nodes 1765: states.by_priority.each do |state| 1766: node = state.draw(graph) 1767: node.fontname = options[:font] 1768: end 1769: 1770: # Add edges 1771: events.each do |event| 1772: edges = event.draw(graph) 1773: edges.each {|edge| edge.fontname = options[:font]} 1774: end 1775: 1776: # Generate the graph 1777: graphvizVersion = Constants::RGV_VERSION.split('.') 1778: file = File.join(options[:path], "#{options[:name]}.#{options[:format]}") 1779: 1780: if graphvizVersion[1] == '9' && graphvizVersion[2] == '0' 1781: outputOptions = {:output => options[:format], :file => file} 1782: else 1783: outputOptions = {options[:format] => file} 1784: end 1785: 1786: graph.output(outputOptions) 1787: graph 1788: rescue LoadError 1789: $stderr.puts 'Cannot draw the machine. `gem install ruby-graphviz` >= v0.9.0 and try again.' 1790: false 1791: end 1792: 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.
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 1221 1221: def event(*names, &block) 1222: options = names.last.is_a?(Hash) ? names.pop : {} 1223: assert_valid_keys(options, :human_name) 1224: 1225: events = add_events(names) 1226: events.each do |event| 1227: event.human_name = options[:human_name] if options.include?(:human_name) 1228: 1229: if block_given? 1230: event.instance_eval(&block) 1231: add_states(event.known_states) 1232: end 1233: 1234: event 1235: end 1236: 1237: events.length == 1 ? events.first : events 1238: 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 1711 1711: def generate_message(name, values = []) 1712: (@messages[name] || self.class.default_messages[name]) % values.map {|value| value.last} 1713: 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 621 621: def initial_state(object) 622: states.fetch(dynamic_initial_state? ? evaluate_method(object, @initial_state) : @initial_state) if instance_variable_defined?('@initial_state') 623: 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 579 579: def initial_state=(new_initial_state) 580: @initial_state = new_initial_state 581: add_states([@initial_state]) unless dynamic_initial_state? 582: 583: # Update all states to reflect the new initial state 584: states.each {|state| state.initial = (state.name == @initial_state)} 585: 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 638 638: def initialize_state(object, options = {}) 639: state = initial_state(object) 640: if state && (options[:force] || initialize_state?(object)) 641: value = state.value 642: 643: if hash = options[:to] 644: hash[attribute.to_s] = value 645: else 646: write(object, :state, value) 647: end 648: end 649: 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 1700 1700: def invalidate(object, attribute, message, values = []) 1701: 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 551 551: def owner_class=(klass) 552: @owner_class = klass 553: 554: # Create modules for extending the class with state/event-specific methods 555: @helper_modules = helper_modules = {:instance => HelperModule.new(self, :instance), :class => HelperModule.new(self, :class)} 556: owner_class.class_eval do 557: extend helper_modules[:class] 558: include helper_modules[:instance] 559: end 560: 561: # Add class-/instance-level methods to the owner class for state initialization 562: unless owner_class < StateMachine::InstanceMethods 563: owner_class.class_eval do 564: extend StateMachine::ClassMethods 565: include StateMachine::InstanceMethods 566: end 567: 568: define_state_initializer if @initialize_state 569: end 570: 571: # Record this machine as matched to the name in the current owner class. 572: # This will override any machines mapped to the same name in any superclasses. 573: owner_class.state_machines[name] = self 574: 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 1693 1693: def paths_for(object, requirements = {}) 1694: PathCollection.new(object, self, requirements) 1695: 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 992 992: def read(object, attribute, ivar = false) 993: attribute = self.attribute(attribute) 994: ivar ? object.instance_variable_get("@#{attribute}") : object.send(attribute) 995: 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 1706 1706: def reset(object) 1707: 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"
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 958 958: def state(*names, &block) 959: options = names.last.is_a?(Hash) ? names.pop : {} 960: assert_valid_keys(options, :value, :cache, :if, :human_name) 961: 962: states = add_states(names) 963: states.each do |state| 964: if options.include?(:value) 965: state.value = options[:value] 966: self.states.update(state) 967: end 968: 969: state.human_name = options[:human_name] if options.include?(:human_name) 970: state.cache = options[:cache] if options.include?(:cache) 971: state.matcher = options[:if] if options.include?(:if) 972: state.context(&block) if block_given? 973: end 974: 975: states.length == 1 ? states.first : states 976: 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 1330 1330: def transition(options) 1331: raise ArgumentError, 'Must specify :on event' unless options[:on] 1332: 1333: branches = [] 1334: event(*Array(options.delete(:on))) { branches << transition(options) } 1335: 1336: branches.length == 1 ? branches.first : branches 1337: 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 1720 1720: def within_transaction(object) 1721: if use_transactions 1722: transaction(object) { yield } 1723: else 1724: yield 1725: end 1726: 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 1012 1012: def write(object, attribute, value, ivar = false) 1013: attribute = self.attribute(attribute) 1014: ivar ? object.instance_variable_set("@#{attribute}", value) : object.send("#{attribute}=", value) 1015: 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 1958 1958: def action_hook 1959: action && owner_class_ancestor_has_method?(:instance, action) ? action : nil 1960: end
Adds a new transition callback of the given type.
# File lib/state_machine/machine.rb, line 2085 2085: def add_callback(type, options, &block) 2086: callbacks[type == :around ? :before : type] << callback = Callback.new(type, options, &block) 2087: add_states(callback.known_states) 2088: callback 2089: end
Tracks the given set of events in the list of all known events for this machine
# File lib/state_machine/machine.rb, line 2108 2108: def add_events(new_events) 2109: new_events.map do |new_event| 2110: unless event = events[new_event] 2111: events << event = Event.new(self, new_event) 2112: end 2113: 2114: event 2115: end 2116: 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 2077 2077: def add_sibling_machine_configs 2078: # Add existing states 2079: sibling_machines.each do |machine| 2080: machine.states.each {|state| states << state unless states[state.name]} 2081: end 2082: end
Tracks the given set of states in the list of all known states for this machine
# File lib/state_machine/machine.rb, line 2093 2093: def add_states(new_states) 2094: new_states.map do |new_state| 2095: unless state = states[new_state] 2096: states << state = State.new(self, new_state) 2097: 2098: # Copy states over to sibling machines 2099: sibling_machines.each {|machine| machine.states << state} 2100: end 2101: 2102: state 2103: end 2104: end
Runs additional initialization hooks. By default, this is a no-op.
# File lib/state_machine/machine.rb, line 1802 1802: def after_initialize 1803: end
Adds helper methods for automatically firing events when an action is invoked
# File lib/state_machine/machine.rb, line 1926 1926: def define_action_helpers 1927: if action_hook 1928: @action_hook_defined = true 1929: define_action_hook 1930: end 1931: 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 1920 1920: def define_action_helpers? 1921: action && !owner_class.state_machines.any? {|name, machine| machine.action == action && machine != self} 1922: 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 1936 1936: def define_action_hook 1937: action_hook = self.action_hook 1938: action = self.action 1939: private_action_hook = owner_class.private_method_defined?(action_hook) 1940: 1941: # Only define helper if it hasn't 1942: 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 1943: end
Adds helper methods for getting information about this state machine‘s events
# File lib/state_machine/machine.rb, line 1872 1872: def define_event_helpers 1873: # Gets the events that are allowed to fire on the current object 1874: define_helper(:instance, attribute(:events)) do |machine, object, *args| 1875: machine.events.valid_for(object, *args).map {|event| event.name} 1876: end 1877: 1878: # Gets the next possible transitions that can be run on the current 1879: # object 1880: define_helper(:instance, attribute(:transitions)) do |machine, object, *args| 1881: machine.events.transitions_for(object, *args) 1882: end 1883: 1884: # Add helpers for tracking the event / transition to invoke when the 1885: # action is called 1886: if action 1887: event_attribute = attribute(:event) 1888: define_helper(:instance, event_attribute) do |machine, object| 1889: # Interpret non-blank events as present 1890: event = machine.read(object, :event, true) 1891: event && !(event.respond_to?(:empty?) && event.empty?) ? event.to_sym : nil 1892: end 1893: 1894: # A roundabout way of writing the attribute is used here so that 1895: # integrations can hook into this modification 1896: define_helper(:instance, "#{event_attribute}=") do |machine, object, value| 1897: machine.write(object, :event, value, true) 1898: end 1899: 1900: event_transition_attribute = attribute(:event_transition) 1901: define_helper :instance, "protected; attr_accessor \#{event_transition_attribute.inspect}\n", __FILE__, __LINE__ + 1 1902: end 1903: end
Adds helper methods for interacting with the state machine, including for states, events, and transitions
# File lib/state_machine/machine.rb, line 1829 1829: def define_helpers 1830: define_state_accessor 1831: define_state_predicate 1832: define_event_helpers 1833: define_path_helpers 1834: define_action_helpers if define_action_helpers? 1835: define_name_helpers 1836: end
Adds helper methods for accessing naming information about states and events on the owner class
# File lib/state_machine/machine.rb, line 1993 1993: def define_name_helpers 1994: # Gets the humanized version of a state 1995: define_helper(:class, "human_#{attribute(:name)}") do |machine, klass, state| 1996: machine.states.fetch(state).human_name(klass) 1997: end 1998: 1999: # Gets the humanized version of an event 2000: define_helper(:class, "human_#{attribute(:event_name)}") do |machine, klass, event| 2001: machine.events.fetch(event).human_name(klass) 2002: end 2003: 2004: # Gets the state name for the current value 2005: define_helper(:instance, attribute(:name)) do |machine, object| 2006: machine.states.match!(object).name 2007: end 2008: 2009: # Gets the human state name for the current value 2010: define_helper(:instance, "human_#{attribute(:name)}") do |machine, object| 2011: machine.states.match!(object).human_name(object.class) 2012: end 2013: end
Adds helper methods for getting information about this state machine‘s available transition paths
# File lib/state_machine/machine.rb, line 1910 1910: def define_path_helpers 1911: # Gets the paths of transitions available to the current object 1912: define_helper(:instance, attribute(:paths)) do |machine, object, *args| 1913: machine.paths_for(object, *args) 1914: end 1915: 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 2020 2020: def define_scopes(custom_plural = nil) 2021: plural = custom_plural || pluralize(name) 2022: 2023: [name, plural].uniq.each do |name| 2024: [:with, :without].each do |kind| 2025: method = "#{kind}_#{name}" 2026: 2027: if scope = send("create_#{kind}_scope", method) 2028: # Converts state names to their corresponding values so that they 2029: # can be looked up properly 2030: define_helper(:class, method) do |machine, klass, *states| 2031: run_scope(scope, machine, klass, states) 2032: end 2033: end 2034: end 2035: end 2036: end
Adds reader/writer methods for accessing the state attribute
# File lib/state_machine/machine.rb, line 1851 1851: def define_state_accessor 1852: attribute = self.attribute 1853: 1854: @helper_modules[:instance].class_eval { attr_reader attribute } unless owner_class_ancestor_has_method?(:instance, attribute) 1855: @helper_modules[:instance].class_eval { attr_writer attribute } unless owner_class_ancestor_has_method?(:instance, "#{attribute}=") 1856: 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 1841 1841: def define_state_initializer 1842: define_helper :instance, "def initialize(*)\nself.class.state_machines.initialize_states(self) { super }\nend\n", __FILE__, __LINE__ + 1 1843: end
Adds predicate method to the owner class for determining the name of the current state
# File lib/state_machine/machine.rb, line 1860 1860: def define_state_predicate 1861: call_super = !!owner_class_ancestor_has_method?(:instance, "#{name}?") 1862: 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 1863: 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 1822 1822: def initialize_state?(object) 1823: value = read(object, :state) 1824: (value.nil? || value.respond_to?(:empty?) && value.empty?) && !states[value, :value] 1825: 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 1966 1966: def owner_class_ancestor_has_method?(scope, method) 1967: superclasses = owner_class.ancestors[1..-1].select {|ancestor| ancestor.is_a?(Class)} 1968: 1969: if scope == :class 1970: # Use singleton classes 1971: current = (class << owner_class; self; end) 1972: superclass = superclasses.first 1973: else 1974: current = owner_class 1975: superclass = owner_class.superclass 1976: end 1977: 1978: # Generate the list of modules that *only* occur in the owner class, but 1979: # were included *prior* to the helper modules, in addition to the 1980: # superclasses 1981: ancestors = current.ancestors - superclass.ancestors + superclasses 1982: ancestors = ancestors[ancestors.index(@helper_modules[scope])..-1].reverse 1983: 1984: # Search for for the first ancestor that defined this method 1985: ancestors.detect do |ancestor| 1986: ancestor = (class << ancestor; self; end) if scope == :class && ancestor.is_a?(Class) 1987: ancestor.method_defined?(method) || ancestor.private_method_defined?(method) 1988: end 1989: 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 2047 2047: def pluralize(word) 2048: word = word.to_s 2049: if word.respond_to?(:pluralize) 2050: word.pluralize 2051: else 2052: "#{name}s" 2053: end 2054: end
Generates the results for the given scope based on one or more states to filter by
# File lib/state_machine/machine.rb, line 2040 2040: def run_scope(scope, machine, klass, states) 2041: values = states.flatten.map {|state| machine.states.fetch(state).value} 2042: scope.call(klass, values) 2043: 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 1811 1811: def sibling_machines 1812: owner_class.state_machines.inject([]) do |machines, (name, machine)| 1813: if machine.attribute == attribute && machine != self 1814: machines << (owner_class.state_machine(name) {}) 1815: end 1816: machines 1817: end 1818: end