This is my refactored version of https://gist.github.com/mileszs/4709536. I am happier with it primarily because all of the parts are now in a single class for each major piece of functionality. It's much easier to understand; when you see in the controller `PagesGenerator.new(document).generate!`, you look in the PagesGenerator class, where you…

categories_generator.rb

class CategoriesGenerator

  def initialize(document, options = {})
    @document = document
    @master_categories = options[:master_categories] || MasterCategory.all

  end

  def generate!
    @master_categories.each do |master_category|
      @document.categories.build(wanted_attributes_from(master_category))
    end
    @document.save!
  end

  private
  def wanted_attributes_from(master_category)
    {
      position: master_category.position,
      name: master_category.name,
      active: master_category.active,
      master_category_id: master_category.id
    }
  end
end

pages_generator.rb

class PagesGenerator

  def initialize(document, options = {})
    @document = document
  end

  def generate!
    @document.categories.each do |category|
      if category.pages.empty?
        category.master_category.master_pages.each do |master_page|
          category.pages.build(wanted_attributes_from(master_page))
        end
        category.save!
      end
    end
  end

  private
  def wanted_attributes_from(master_page)
    {
      position: master_page.position,
      name: master_page.name,
      index_page: master_page.index_page,
      master_page_id: master_page.id
    }
  end
end

master_page.attributes.slice(*%w[position name index_page master_page_id])

If you need keys as symbols tack on a .symbolize_keys too maybe?

Are these two classes being used in succession? e.g.

@document = Document.new
CategoryGenerator.new(@document).generate!
PagesGenerator.new(@document).generate!

Or are the uses separated in time/space?

Looks good overall -- testable and flexible, it seems.

@shipstar: Separately. There's a wizard-ish flow, and these things are called in separate steps.

@veloper: Ah, thanks! What's sad is I was doing essentially that in the old one.