Module: StateMachine::Integrations::DataMapper::Observer

Includes:
MatcherHelpers
Defined in:
lib/state_machine/integrations/data_mapper/observer.rb

Overview

Adds support for creating before/after transition callbacks within a DataMapper observer. These callbacks behave very similar to before/after hooks during save/update/destroy/etc., but with the following modifications:

  • Each callback can define a set of transition conditions (i.e. guards)

that must be met in order for the callback to get invoked.

  • An additional transition parameter is available that provides

contextual information about the event (see StateMachine::Transition for more information)

To define a single observer for multiple state machines:

class StateMachineObserver
  include DataMapper::Observer

  observe Vehicle, Switch, Project

  after_transition do |transition|
    Audit.log(self, transition)
  end
end

Requirements

To use this feature of the DataMapper integration, the dm-observer library must be available. This can be installed either directly or indirectly through dm-more. When loading DataMapper, be sure to load the dm-observer library as well like so:

require 'rubygems'
require 'dm-core'
require 'dm-observer'

If dm-observer is not available, then this feature will be skipped.

Instance Method Summary collapse

Methods included from MatcherHelpers

#all, #same

Instance Method Details

#after_transition(*args, &block) ⇒ Object

Creates a callback that will be invoked after a transition is performed so long as the given configuration options match the transition.

See before_transition for a description of the possible configurations for defining callbacks.



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# File 'lib/state_machine/integrations/data_mapper/observer.rb', line 103

def after_transition(*args, &block)
  add_transition_callback(:after, *args, &block)
end

#before_transition(*args, &block) ⇒ Object

Creates a callback that will be invoked before a transition is performed, so long as the given configuration options match the transition. Each part of the transition (event, to state, from state) must match in order for the callback to get invoked.

See StateMachine::Machine#before_transition for more information about the various configuration options available.

Examples

class Vehicle
  include DataMapper::Resource

  property :id, Serial
  property :state, :String

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

class VehicleObserver
  include DataMapper::Observer

  observe Vehicle

  before :save do
    # log message
  end

  # Target all state machines
  before_transition :parked => :idling, :on => :ignite do
    # put on seatbelt
  end

  # Target a specific state machine
  before_transition :state, any => :idling do
    # put on seatbelt
  end

  # Target all state machines without requirements
  before_transition do |transition|
    # log message
  end
end

Note that in each of the above before_transition callbacks, the callback is executed within the context of the object (i.e. the Vehicle instance being transition). This means that self refers to the vehicle record within each callback block.



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# File 'lib/state_machine/integrations/data_mapper/observer.rb', line 93

def before_transition(*args, &block)
  add_transition_callback(:before, *args, &block)
end