Class: StateMachines::Event

Inherits:
Object
  • Object
show all
Includes:
MatcherHelpers
Defined in:
lib/state_machines/event.rb

Overview

An event defines an action that transitions an attribute from one state to another. The state that an attribute is transitioned to depends on the branches configured for the event.

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods included from MatcherHelpers

#all, #same

Constructor Details

#initialize(machine, name, options = nil, human_name: nil, **extra_options) ⇒ Event

Creates a new event within the context of the given machine

Configuration options:

  • :human_name - The human-readable version of this event’s name



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

def initialize(machine, name, options = nil, human_name: nil, **extra_options) # :nodoc:
  # Handle both old hash style and new kwargs style for backward compatibility
  if options.is_a?(Hash)
    # Old style: initialize(machine, name, {human_name: 'Custom Name'})
    StateMachines::OptionsValidator.assert_valid_keys!(options, :human_name)
    human_name = options[:human_name]
  else
    # New style: initialize(machine, name, human_name: 'Custom Name')
    raise ArgumentError, "Unexpected positional argument: #{options.inspect}" unless options.nil?

    StateMachines::OptionsValidator.assert_valid_keys!(extra_options, :human_name) unless extra_options.empty?
  end

  @machine = machine
  @name = name
  @qualified_name = machine.namespace ? :"#{name}_#{machine.namespace}" : name
  @human_name = human_name || @name.to_s.tr('_', ' ')
  reset

  # Output a warning if another event has a conflicting qualified name
  if (conflict = machine.owner_class.state_machines.detect { |_other_name, other_machine| other_machine != @machine && other_machine.events[qualified_name, :qualified_name] })
    _name, other_machine = conflict
    warn "Event #{qualified_name.inspect} for #{machine.name.inspect} is already defined in #{other_machine.name.inspect}"
  else
    add_actions
  end
end

Instance Attribute Details

#branches ⇒ Object (readonly)

The list of branches that determine what state this event transitions objects to when fired



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

def branches
  @branches
end

#human_name(klass = @machine.owner_class) ⇒ Object

Transforms the event name into a more human-readable format, such as “turn on” instead of “turn_on”



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# File 'lib/state_machines/event.rb', line 74

def human_name(klass = @machine.owner_class)
  @human_name.is_a?(Proc) ? @human_name.call(self, klass) : @human_name
end

#known_states ⇒ Object (readonly)

A list of all of the states known to this event using the configured branches/transitions as the source



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

def known_states
  @known_states
end

#machine ⇒ Object

The state machine for which this event is defined



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# File 'lib/state_machines/event.rb', line 13

def machine
  @machine
end

#name ⇒ Object (readonly)

The name of the event



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# File 'lib/state_machines/event.rb', line 16

def name
  @name
end

#qualified_name ⇒ Object (readonly)

The fully-qualified name of the event, scoped by the machine’s namespace



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# File 'lib/state_machines/event.rb', line 19

def qualified_name
  @qualified_name
end

Instance Method Details

#can_fire?(object, requirements = {}) ⇒ Boolean

Determines whether any transitions can be performed for this event based on the current state of the given object.

If the event can’t be fired, then this will return false, otherwise true.

Note that this will not take the object context into account. Although a transition may be possible based on the state machine definition, object-specific behaviors (like validations) may prevent it from firing.

Returns:

  • (Boolean) 


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

def can_fire?(object, requirements = {})
  !transition_for(object, requirements).nil?
end

#context ⇒ Object

Evaluates the given block within the context of this event. This simply provides a DSL-like syntax for defining transitions.



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# File 'lib/state_machines/event.rb', line 80

def context(&)
  instance_eval(&)
end

#draw(graph, options = {}, io = $stdout) ⇒ Object 



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

def draw(graph, options = {}, io = $stdout)
  machine.renderer.draw_event(self, graph, options, io)
end

#fire(object, *event_args) ⇒ Object

Attempts to perform the next available transition on the given object. If no transitions can be made, then this will return false, otherwise true.

Any additional arguments are passed to the StateMachines::Transition#perform instance method.



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# File 'lib/state_machines/event.rb', line 166

def fire(object, *event_args)
  machine.reset(object)

  if (transition = transition_for(object, {}, *event_args))
    transition.perform(*event_args)
  else
    on_failure(object, *event_args)
    false
  end
end

#initialize_copy(orig) ⇒ Object

Creates a copy of this event in addition to the list of associated branches to prevent conflicts across events within a class hierarchy.



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# File 'lib/state_machines/event.rb', line 66

def initialize_copy(orig) # :nodoc:
  super
  @branches = @branches.dup
  @known_states = @known_states.dup
end

#inspect ⇒ Object

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

For example,

event = StateMachines::Event.new(machine, :park)
event.transition all - :idling => :parked, :idling => same
event   # => #<StateMachines::Event name=:park transitions=[all - :idling => :parked, :idling => same]>



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# File 'lib/state_machines/event.rb', line 208

def inspect
  transitions = branches.flat_map do |branch|
    branch.state_requirements.map do |state_requirement|
      "#{state_requirement[:from].description} => #{state_requirement[:to].description}"
    end
  end.join(', ')

  "#<#{self.class} name=#{name.inspect} transitions=[#{transitions}]>"
end

#on_failure(object, *args) ⇒ Object

Marks the object as invalid and runs any failure callbacks associated with this event. This should get called anytime this event fails to transition.



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# File 'lib/state_machines/event.rb', line 179

def on_failure(object, *args)
  state = machine.states.match!(object)
  machine.invalidate(object, :state, :invalid_transition, [[:event, human_name(object.class)], [:state, state.human_name(object.class)]])

  transition = Transition.new(object, machine, name, state.name, state.name)
  transition.args = args if args.any?
  transition.run_callbacks(before: false)
end

#reset ⇒ Object

Resets back to the initial state of the event, with no branches / known states associated. This allows you to redefine an event in situations where you either are re-using an existing state machine implementation or are subclassing machines.



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# File 'lib/state_machines/event.rb', line 192

def reset
  @branches = []
  @known_states = []
end

#transition(options) ⇒ Object

Creates a new transition that determines what to change the current state to when this event fires.

Since this transition is being defined within an event context, you do not need to specify the :on option for the transition. For example:

state_machine do
  event :ignite do
    transition :parked => :idling, :idling => same, :if => :seatbelt_on? # Transitions to :idling if seatbelt is on
    transition all => :parked, :unless => :seatbelt_on?                  # Transitions to :parked if seatbelt is off
  end
end

See StateMachines::Machine#transition for a description of the possible configurations for defining transitions.

Raises:

  • (ArgumentError) 


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# File 'lib/state_machines/event.rb', line 100

def transition(options)
  raise ArgumentError, 'Must specify as least one transition requirement' if options.empty?

  # Only a certain subset of explicit options are allowed for transition
  # requirements
  StateMachines::OptionsValidator.assert_valid_keys!(options, :from, :to, :except_from, :except_to, :if, :unless) if (options.keys - %i[from to on except_from except_to except_on if unless]).empty?

  branches << branch = Branch.new(options.merge(on: name))
  @known_states |= branch.known_states
  branch
end

#transition_for(object, requirements = {}, *event_args) ⇒ Object

Finds and builds the next transition that can be performed on the given object. If no transitions can be made, then this will return nil.

Valid requirement options:

  • :from - One or more states being transitioned from. If none are specified, then this will be the object’s current state.

  • :to - One or more states being transitioned to. If none are specified, then this will match any to state.

  • :guard - Whether to guard transitions with the if/unless conditionals defined for each one. Default is true.

Event arguments are passed to guard conditions if they accept multiple parameters.



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# File 'lib/state_machines/event.rb', line 136

def transition_for(object, requirements = {}, *event_args)
  StateMachines::OptionsValidator.assert_valid_keys!(requirements, :from, :to, :guard)
  requirements[:from] = machine.states.match!(object).name unless (custom_from_state = requirements.include?(:from))

  branches.each do |branch|
    next unless (match = branch.match(object, requirements, event_args))

    # Branch allows for the transition to occur
    from = requirements[:from]
    to = if match[:to].is_a?(LoopbackMatcher)
           from
         else
           values = requirements.include?(:to) ? [requirements[:to]].flatten : [from] | machine.states.map { |state| state.name }

           match[:to].filter(values).first
         end

    return Transition.new(object, machine, name, from, to, !custom_from_state)
  end

  # No transition matched
  nil
end