workflow.rb

WorkflowEventsController < ApplicationController
  # . . . 
  def create
    workflow_event = WorkflowEvent.new(params[:workflow_event])
    @some_model = SomeModel.find(params[:some_model_id]
    SomeWorkflow.new(current_user, @some_model).handle(workflow_event) do |result|
      result.on_success { render :template => 'success' }
      result.on_failure { render :template => 'failure' }
    end
  end
  # . . . 
end

#
# example workflow returning multiple results
#
class SomeWorkflow < Workflow

  include SimpleStates

  states :created, :started, :finished

  def startable?
    return true if @subject.has_claim?
    @subject.errors[:base] << 'There must be an attached labor or part claim.'
    false
  end

  event :start,   :to => :started,  :if => :startable?, :from => [:created]
  event :finish,  :to => :finished, :if => nil,         :from => [:started]

  # you can call return_#{any_result_class}  This works a bit like 
  # rendering in controllers.  If you don't call at least one there
  # will be an exception
  def start
    if unspecifified_condition
      return_success         # causes the result in the controller's handle block to yield to on_failure
    else
      return_failure('foo')  # causes the result in the controller's handle block to yield to on_failure and pass in 'foo'
    end
  end

  # Except if you don't define the method at all then it will automatically return what 
  # ever is defined using as the default result.  So we never defined a 'finish' method.

  # So if we define the default like so

  default_result :return_success

  # The 'finish' method that doesn't exist will behave like this
  #
  #   def finish
  #     return_success
  #   end

end