Class: StateMachines::Transition

Inherits:
Object
  • Object
show all
Defined in:
lib/state_machines/transition.rb

Overview

A transition represents a state change for a specific attribute.

Transitions consist of:

  • An event

  • A starting state

  • An ending state

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(object, machine, event, from_name, to_name, read_state = true) ⇒ Transition

Creates a new, specific transition



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# File 'lib/state_machines/transition.rb', line 39

def initialize(object, machine, event, from_name, to_name, read_state = true) # :nodoc:
  @object = object
  @machine = machine
  @args = []
  @transient = false
  @paused_fiber = nil
  @resuming = false
  @continuation_block = nil

  @event = machine.events.fetch(event)
  @from_state = machine.states.fetch(from_name)
  @from = read_state ? machine.read(object, :state) : @from_state.value
  @to_state = machine.states.fetch(to_name)
  @to = @to_state.value

  reset
end

Instance Attribute Details

#args ⇒ Object

The arguments passed in to the event that triggered the transition (does not include the run_action boolean argument if specified)



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# File 'lib/state_machines/transition.rb', line 30

def args
  @args
end

#from ⇒ Object (readonly)

The original state value before the transition



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# File 'lib/state_machines/transition.rb', line 23

def from
  @from
end

#machine ⇒ Object (readonly)

The state machine for which this transition is defined



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# File 'lib/state_machines/transition.rb', line 20

def machine
  @machine
end

#object ⇒ Object (readonly)

The object being transitioned



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# File 'lib/state_machines/transition.rb', line 17

def object
  @object
end

#result ⇒ Object (readonly)

The result of invoking the action associated with the machine



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# File 'lib/state_machines/transition.rb', line 33

def result
  @result
end

#to ⇒ Object (readonly)

The new state value after the transition



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# File 'lib/state_machines/transition.rb', line 26

def to
  @to
end

#transient=(value) ⇒ Object (writeonly)

Whether the transition is only existing temporarily for the object



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# File 'lib/state_machines/transition.rb', line 36

def transient=(value)
  @transient = value
end

Instance Method Details

#==(other) ⇒ Object

Determines equality of transitions by testing whether the object, states, and event involved in the transition are equal



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# File 'lib/state_machines/transition.rb', line 295

def ==(other)
  other.instance_of?(self.class) &&
    other.object == object &&
    other.machine == machine &&
    other.from_name == from_name &&
    other.to_name == to_name &&
    other.event == event
end

#action ⇒ Object

The action that will be run when this transition is performed



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# File 'lib/state_machines/transition.rb', line 63

def action
  machine.action
end

#attribute ⇒ Object

The attribute which this transition’s machine is defined for



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# File 'lib/state_machines/transition.rb', line 58

def attribute
  machine.attribute
end

#attributes ⇒ Object

A hash of all the core attributes defined for this transition with their names as keys and values of the attributes as values.

Example

machine = StateMachine.new(Vehicle)
transition = StateMachines::Transition.new(Vehicle.new, machine, :ignite, :parked, :idling)
transition.attributes   # => {:object => #<Vehicle:0xb7d60ea4>, :attribute => :state, :event => :ignite, :from => 'parked', :to => 'idling'}



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# File 'lib/state_machines/transition.rb', line 139

def attributes
  @attributes ||= { object: object, attribute: attribute, event: event, from: from, to: to }
end

#event ⇒ Object

The event that triggered the transition



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# File 'lib/state_machines/transition.rb', line 68

def event
  @event.name
end

#from_name ⇒ Object

The state name before the transition



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# File 'lib/state_machines/transition.rb', line 83

def from_name
  @from_state.name
end

#human_event ⇒ Object

The human-readable name of the event that triggered the transition



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# File 'lib/state_machines/transition.rb', line 78

def human_event
  @event.human_name(@object.class)
end

#human_from_name ⇒ Object

The human-readable state name before the transition



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# File 'lib/state_machines/transition.rb', line 93

def human_from_name
  @from_state.human_name(@object.class)
end

#human_to_name ⇒ Object

The new human-readable state name after the transition



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# File 'lib/state_machines/transition.rb', line 108

def human_to_name
  @to_state.human_name(@object.class)
end

#inspect ⇒ Object

Generates a nicely formatted description of this transitions’s contents.

For example,

transition = StateMachines::Transition.new(object, machine, :ignite, :parked, :idling)
transition   # => #<StateMachines::Transition attribute=:state event=:ignite from="parked" from_name=:parked to="idling" to_name=:idling>



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# File 'lib/state_machines/transition.rb', line 310

def inspect
  "#<#{self.class} #{%w[attribute event from from_name to to_name].map { |attr| "#{attr}=#{send(attr).inspect}" } * ' '}>"
end

#loopback? ⇒ Boolean

Does this transition represent a loopback (i.e. the from and to state are the same)

Example

machine = StateMachine.new(Vehicle)
StateMachines::Transition.new(Vehicle.new, machine, :park, :parked, :parked).loopback?   # => true
StateMachines::Transition.new(Vehicle.new, machine, :park, :idling, :parked).loopback?   # => false

Returns:

  • (Boolean) 


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# File 'lib/state_machines/transition.rb', line 120

def loopback?
  from_name == to_name
end

#paused? ⇒ Boolean

Checks whether this transition is currently paused. Returns true if there is a paused fiber, false otherwise.

Returns:

  • (Boolean) 


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# File 'lib/state_machines/transition.rb', line 316

def paused?
  @paused_fiber&.alive? || false
end

#perform(*args) ⇒ Object

Runs the actual transition and any before/after callbacks associated with the transition. The action associated with the transition/machine can be skipped by passing in false.

Examples

class Vehicle
  state_machine :action => :save do
    ...
  end
end

vehicle = Vehicle.new
transition = StateMachines::Transition.new(vehicle, machine, :ignite, :parked, :idling)
transition.perform                              # => Runs the +save+ action after setting the state attribute
transition.perform(false)                       # => Only sets the state attribute
transition.perform(run_action: false)           # => Only sets the state attribute
transition.perform(Time.now)                    # => Passes in additional arguments and runs the +save+ action
transition.perform(Time.now, false)             # => Passes in additional arguments and only sets the state attribute
transition.perform(Time.now, run_action: false) # => Passes in additional arguments and only sets the state attribute



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# File 'lib/state_machines/transition.rb', line 163

def perform(*args)
  run_action = case args.last
               in true | false
                 args.pop
               in { run_action: }
                 args.last.delete(:run_action)
               else
                 true
               end

  self.args = args

  # Run the transition
  !!TransitionCollection.new([self], { use_transactions: machine.use_transactions, actions: run_action }).perform
end

#persist ⇒ Object

Transitions the current value of the state to that specified by the transition. Once the state is persisted, it cannot be persisted again until this transition is reset.

Example

class Vehicle
  state_machine do
    event :ignite do
      transition :parked => :idling
    end
  end
end

vehicle = Vehicle.new
transition = StateMachines::Transition.new(vehicle, Vehicle.state_machine, :ignite, :parked, :idling)
transition.persist

vehicle.state   # => 'idling'



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# File 'lib/state_machines/transition.rb', line 248

def persist
  return if @persisted

  machine.write(object, :state, to)
  @persisted = true
end

#qualified_event ⇒ Object

The fully-qualified name of the event that triggered the transition



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# File 'lib/state_machines/transition.rb', line 73

def qualified_event
  @event.qualified_name
end

#qualified_from_name ⇒ Object

The fully-qualified state name before the transition



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# File 'lib/state_machines/transition.rb', line 88

def qualified_from_name
  @from_state.qualified_name
end

#qualified_to_name ⇒ Object

The new fully-qualified state name after the transition



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# File 'lib/state_machines/transition.rb', line 103

def qualified_to_name
  @to_state.qualified_name
end

#reset ⇒ Object

Resets any tracking of which callbacks have already been run and whether the state has already been persisted



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# File 'lib/state_machines/transition.rb', line 286

def reset
  @before_run = @persisted = @after_run = false
  @paused_fiber = nil
  @resuming = false
  @continuation_block = nil
end

#resumable? ⇒ Boolean

Checks whether this transition has a paused fiber that can be resumed. Returns true if there is a paused fiber, false otherwise.

Note: The actual resuming happens automatically when run_callbacks is called again on a transition with a paused fiber.

Returns:

  • (Boolean) 


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# File 'lib/state_machines/transition.rb', line 325

def resumable?
  paused?
end

#resume!(&block) ⇒ Object

Manually resumes the execution of a previously paused callback. Returns true if the transition was successfully resumed and completed, false if there was no paused fiber, and raises an exception if the transition was halted.



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# File 'lib/state_machines/transition.rb', line 333

def resume!(&block)
  return false unless paused?

  # Store continuation block if provided
  @continuation_block = block if block_given?

  # Run the pausable block which will resume the fiber
  halted = pausable { true }

  # Return whether the transition completed successfully
  !halted
end

#rollback ⇒ Object

Rolls back changes made to the object’s state via this transition. This will revert the state back to the from value.

Example

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

vehicle = Vehicle.new     # => #<Vehicle:0xb7b7f568 @state="parked">
transition = StateMachines::Transition.new(vehicle, Vehicle.state_machine, :ignite, :parked, :idling)

# Persist the new state
vehicle.state             # => "parked"
transition.persist
vehicle.state             # => "idling"

# Roll back to the original state
transition.rollback
vehicle.state             # => "parked"



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# File 'lib/state_machines/transition.rb', line 279

def rollback
  reset
  machine.write(object, :state, from)
end

#run_callbacks(options = {}, &block) ⇒ Object

Runs the before / after callbacks for this transition. If a block is provided, then it will be executed between the before and after callbacks.

Configuration options:

  • before - Whether to run before callbacks.

  • after - Whether to run after callbacks. If false, then any around callbacks will be paused until called again with after enabled. Default is true.

This will return true if all before callbacks gets executed. After callbacks will not have an effect on the result.



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# File 'lib/state_machines/transition.rb', line 197

def run_callbacks(options = {}, &block)
  options = { before: true, after: true }.merge(options)

  # If we have a paused fiber and we're not trying to resume (after: false),
  # this is an idempotent call on an already-paused transition. Just return true.
  return true if @paused_fiber&.alive? && !options[:after]

  # Extract pausable options
  pausable_options = options.key?(:fiber) ? { fiber: options[:fiber] } : {}

  # Check if we're resuming from a pause
  if @paused_fiber&.alive? && options[:after]
    # Resume the paused fiber
    # Don't reset @success when resuming - preserve the state from the pause
    # Store the block for later execution
    @continuation_block = block if block_given?
    halted = pausable(pausable_options) { true }
  else
    @success = false
    # For normal execution (not pause/resume), default to success
    # The action block will override this if needed
    halted = pausable(pausable_options) { before(options[:after], &block) } if options[:before]
  end

  # After callbacks are only run if:
  # * An around callback didn't halt after yielding OR the run failed
  # * They're enabled or the run didn't succeed
  after if (!(@before_run && halted) || !@success) && (options[:after] || !@success)

  @before_run
end

#to_name ⇒ Object

The new state name after the transition



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# File 'lib/state_machines/transition.rb', line 98

def to_name
  @to_state.name
end

#transient? ⇒ Boolean

Is this transition existing for a short period only? If this is set, it indicates that the transition (or the event backing it) should not be written to the object if it fails.

Returns:

  • (Boolean) 


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# File 'lib/state_machines/transition.rb', line 127

def transient?
  @transient
end

#within_transaction ⇒ Object

Runs a block within a transaction for the object being transitioned. By default, transactions are a no-op unless otherwise defined by the machine’s integration.



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# File 'lib/state_machines/transition.rb', line 182

def within_transaction(&)
  machine.within_transaction(object, &)
end