Moving model creation/update to a separate class

card_creator.rb

class CardCreator < Struct.new(:listener)                                           
  class Failed < RuntimeError                                                       
    attr_accessor :model                                                            
                                                                                    
    def initialize(model)                                                           
      @model = model                                                                
    end                                                                             
  end                                                                               
                                                                                    
  def self.create(iteration, attributes)                                            
    card = iteration.cards.build(attributes)                                        
    card.save!                                                                      
  rescue ActiveRecord::RecordInvalid                                                
    raise Failed.new(card)                                                          
  else                                                                              
    card                                                                            
  end                                                                               
end

cards_controller.rb

class CardsController < ApplicationController
  def create                                                                             
    card = CardCreator.create(project.backlog, card_params)                              
    redirect_to planning_path(card.iteration.project)                                    
  rescue CardCreator::Failed => e                                                        
    @card = e.model                                                                      
    @title = 'New card'                                                                  
    flash.now[:alert] = 'Your card needs a title'                                        
    render :action => 'new'                                                              
  end
end