warranty_claim_events_controller.rb

class WarrantyClaimEventsController < ApplicationController
  # . . .
  def create
    @warranty_claim = WarrantyClaim.find(params[:warranty_claim_id])
    WarrantyClaimWorkflow.new(current_user.id, @warranty_claim).send(params[:warranty_claim_event][:name]) do |result|
      result.on_success do |message| 
        flash[:notice] = "warranty claim successfully updated" 
        redirect_to warranty_claim_path(@warranty_claim)
      end
      result.on_failure do
        render :template => 'warranty_claims/show'
      end
    end
  end
  # . . . 
end

workflow.rb

class WarrantyClaimWorkflow
  # . . . 
  def submit_for_review
    raise InvalidWorkflowEvent unless valid_prior_states.include?(@warranty_claim.state)
    if validate_ready_to_submit_for_review
      WarrantyClaimEvent.transaction do
        @warranty_claim.update_attribute(:state, :submitted)
        @warranty_claim.warranty_claim_events.create!(:user_id => @user_id, :event => :submit_for_review)
      end
      yield SuccessResult.new
    else
      yield FailureResult.new
    end
  end

  def cancel_claim
    # . . .
  end

  def submit_for_credit
    # . . .
  end
  # . . .
end

workflow_results.rb

class WarrantyClaimWorkflow
  class InvalidWorkflowEvent < StandardError; end
  class SuccessResult
    def on_success; yield end
    def on_failure; end
  end
  class FailureResult
    def on_success; end
    def on_failure; yield end
  end
end