rails-docstore/app/helpers/categories_helper.rb

module CategoriesHelper
  def category_collection_select
    cats = []
    Category.where(user_id: @category.user_id).each do |cat|
      s = cat.name
      cat_parent = Category.find_by(id: cat.parent_id)

      while cat_parent != nil do
        s = cat_parent.name + "/" + s
        cat_parent = Category.find_by(id: cat_parent.parent_id)
      end

      cat.name = s
      cats.push cat
    end
    collection_select(:category, :parent_id, cats.sort_by(&:name), :id, :name, include_blank: true)
  end


end