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

Class Method 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


38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
# File 'lib/state_machines/transition.rb', line 38

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

#argsObject

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


23
24
25
# File 'lib/state_machines/transition.rb', line 23

def args
  @args
end

#fromObject (readonly)

The original state value before the transition


16
17
18
# File 'lib/state_machines/transition.rb', line 16

def from
  @from
end

#machineObject (readonly)

The state machine for which this transition is defined


13
14
15
# File 'lib/state_machines/transition.rb', line 13

def machine
  @machine
end

#objectObject (readonly)

The object being transitioned


10
11
12
# File 'lib/state_machines/transition.rb', line 10

def object
  @object
end

#resultObject (readonly)

The result of invoking the action associated with the machine


26
27
28
# File 'lib/state_machines/transition.rb', line 26

def result
  @result
end

#toObject (readonly)

The new state value after the transition


19
20
21
# File 'lib/state_machines/transition.rb', line 19

def to
  @to
end

#transient=(value) ⇒ Object (writeonly)

Whether the transition is only existing temporarily for the object


29
30
31
# File 'lib/state_machines/transition.rb', line 29

def transient=(value)
  @transient = value
end

Class Method Details

.pause_supported?Boolean

Determines whether the current ruby implementation supports pausing and resuming transitions

Returns:

  • (Boolean)

33
34
35
# File 'lib/state_machines/transition.rb', line 33

def self.pause_supported?
  %w(ruby maglev).include?(RUBY_ENGINE)
end

Instance Method Details

#==(other) ⇒ Object

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


264
265
266
267
268
269
270
271
# File 'lib/state_machines/transition.rb', line 264

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

#actionObject

The action that will be run when this transition is performed


60
61
62
# File 'lib/state_machines/transition.rb', line 60

def action
  machine.action
end

#attributeObject

The attribute which this transition's machine is defined for


55
56
57
# File 'lib/state_machines/transition.rb', line 55

def attribute
  machine.attribute
end

#attributesObject

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'}

136
137
138
# File 'lib/state_machines/transition.rb', line 136

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

#eventObject

The event that triggered the transition


65
66
67
# File 'lib/state_machines/transition.rb', line 65

def event
  @event.name
end

#from_nameObject

The state name before the transition


80
81
82
# File 'lib/state_machines/transition.rb', line 80

def from_name
  @from_state.name
end

#human_eventObject

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


75
76
77
# File 'lib/state_machines/transition.rb', line 75

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

#human_from_nameObject

The human-readable state name before the transition


90
91
92
# File 'lib/state_machines/transition.rb', line 90

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

#human_to_nameObject

The new human-readable state name after the transition


105
106
107
# File 'lib/state_machines/transition.rb', line 105

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

#inspectObject

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>

279
280
281
# File 'lib/state_machines/transition.rb', line 279

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)

117
118
119
# File 'lib/state_machines/transition.rb', line 117

def loopback?
  from_name == to_name
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(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

158
159
160
161
162
163
164
# File 'lib/state_machines/transition.rb', line 158

def perform(*args)
  run_action = [true, false].include?(args.last) ? args.pop : true
  self.args = args
  
  # Run the transition
  !!TransitionCollection.new([self], {use_transactions: machine.use_transactions, actions: run_action}).perform
end

#persistObject

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'

219
220
221
222
223
224
# File 'lib/state_machines/transition.rb', line 219

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

#qualified_eventObject

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


70
71
72
# File 'lib/state_machines/transition.rb', line 70

def qualified_event
  @event.qualified_name
end

#qualified_from_nameObject

The fully-qualified state name before the transition


85
86
87
# File 'lib/state_machines/transition.rb', line 85

def qualified_from_name
  @from_state.qualified_name
end

#qualified_to_nameObject

The new fully-qualified state name after the transition


100
101
102
# File 'lib/state_machines/transition.rb', line 100

def qualified_to_name
  @to_state.qualified_name
end

#resetObject

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


257
258
259
260
# File 'lib/state_machines/transition.rb', line 257

def reset
  @before_run = @persisted = @after_run = false
  @paused_block = nil
end

#rollbackObject

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"

250
251
252
253
# File 'lib/state_machines/transition.rb', line 250

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.


186
187
188
189
190
191
192
193
194
195
196
197
198
# File 'lib/state_machines/transition.rb', line 186

def run_callbacks(options = {}, &block)
  options = {:before => true, :after => true}.merge(options)
  @success = false
  
  halted = pausable { before(options[:after], &block) } if options[:before]
  
  # After callbacks are only run if:
  # * An around callback didn't halt after yielding
  # * They're enabled or the run didn't succeed
  after if !(@before_run && halted) && (options[:after] || !@success)
  
  @before_run
end

#to_nameObject

The new state name after the transition


95
96
97
# File 'lib/state_machines/transition.rb', line 95

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)

124
125
126
# File 'lib/state_machines/transition.rb', line 124

def transient?
  @transient
end

#within_transactionObject

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.


169
170
171
172
173
# File 'lib/state_machines/transition.rb', line 169

def within_transaction
  machine.within_transaction(object) do
    yield
  end
end