Query para trazer as descricoes

color.rb

class Color < ActiveRecord::Base
	has_many :variations
	validates :cod,
            :presence => true,
            :uniqueness => true
    validates :descricao,
            :presence => true,
            :uniqueness => true
end

product.rb

class Product < ActiveRecord::Base
	has_many :variations
	validates :cod,
            :presence => true,
            :uniqueness => true
    validates :descricao,
            :presence => true,
            :uniqueness => true
    validates :price,:numericality => true
end

size.rb

class Size < ActiveRecord::Base
	has_many :variations
    validates :descricao,
            :presence => true,
            :uniqueness => true
end

variation.rb

class Variation < ActiveRecord::Base
	belongs_to :product
	belongs_to :size
	belongs_to :color
	before_save :gera_cod_barras
	validates :product_id,
            :presence => true
    validates :size_id,
            :presence => true
    validates :color_id,
            :presence => true
    validates :quantity,
    		:presence => true,
    		:numericality => true
    		validates_uniqueness_of :product_id, scope: [:size_id, :color_id]


	# def barcode(barcode)
	#   outputter = Barby::CairoOutputter.new(barcode)
	# end
	# include HasBarcode

	#   has_barcode :barcode,
	#     :outputter => :svg,
	#     :type => :code_39,
	#     :value =>  "1234567"
	    # Proc.new { |p| "#{p.barcode}" }
	# def number
	#   self.barcode
	# end

	def gera_cod_barras
		produto = self.product.cod
		cor = self.color.cod
		tamanho = self.size.descricao
		cod_barras = produto + tamanho + cor
		self.barcode = cod_barras
	end
	# def self.to_csv
	# 	attributes = %w{barcode}
	# 	CSV.generate do |csv|
	# 		csv << attributes

	# 		all.each do |variation|
	# 			csv << variation.attributes.values_at(*attributes)
	# 		end
	# 	end

	# end

	def self.to_csv(options = {})
	  CSV.generate(options) do |csv|
	    csv.add_row column_names
	    all.each do |variation|
	      values = variation.attributes.values
	      csv.add_row values
	    end
	  end
	end
end

variations_controller.rb

class VariationsController < ApplicationController
  before_action :set_variation, only: [:show, :edit, :update, :destroy]
  # require 'barby/outputter/cairo_outputter'
  # def barcode_output( order )
  #       barcode_string = order.barcode
  #       barcode = Barby::Code128B.new(barcode_string)

  #       # PNG OUTPUT
  #       data = barcode.to_image(height: 15, margin: 5).to_data_url
  #     end
  # GET /variations
  # GET /variations.json
  def export
    @data = Variation.order(:created_at)
    # @data = Variation.select(:barcode).order(created_at: :desc)
      respond_to do |format|
        format.html { redirect_to root_url }
        format.csv { send_data @data.to_csv }
      end

  end
  def index

    # @barcode = Barby::Code128B.new("160P10") rescue nil
    # @outputter = Barby::HtmlOutputter.new(@barcode)
    # @blob = Barby::PngOutputter.new(@barcode).to_png #Raw PNG data

    # @barcode = Barby::HtmlOutputter.new('160P10')
    # @barcode_for_html = Barby::HtmlOutputter.new(@barcode)
    @variations = Variation.all
    # @import = Variation::Import.new
    respond_to do |format|
      format.html
      format.csv { send_data @variations}
    end
    # def import
    #   @import = Variation::Import.new variation_import_params
    #   if @import.save
    #     redirect_to variations_path, notice: "Importados #{@import.imported_count} Cod Barras"
    #   else
    #     @variations = Variation.all
    #     flash[:alert] = "Foram encontrados #{@import.errors.count} erros no CSV"
    #     render action: index
    #   end


    # end
    # require 'barby/outputter/png_outputter'
    # blob = Barby::PngOutputter.new("12345").to_png #Raw PNG data
    # File.open('barcode.png', 'wb'){|f| f.write blob }
    #Convenience method
    # File.open('barcode2.png', 'wb'){|f| f.write barcode.to_png }
    # @barcode = Barby::EAN13.new('000000000')
    # @barcode_for_html = Barby::CairoOutputter.new("0123456789")

    # Variation.new.barcode       # => Barby::Code39 object
    # Variation.new.barcode_data  # => <Barby::Code39 object>.to_png
  end

  # GET /variations/1
  # GET /variations/1.json
  def show
  end

  # GET /variations/new
  def new
    @variation = Variation.new
    @variacoes_js = Variation.joins(:color, :product, :size).includes(:color, :product, :size)
    # # ActiveRecord::Base.include_root_in_json = true
    gon.variacoes = @variacoes_js.to_json
    # @tamanhos = Size.order(:descricao).select(:id,:descricao)
    # gon.tamanhos = @tamanhos.to_json
    # @produtos = Product.order(:cod).select(:cod,:descricao)
    # gon.produtos = @produtos.to_json

  end

  # GET /variations/1/edit
  def edit
  end

  # POST /variations
  # POST /variations.json
  def create
    @variation = Variation.new(variation_params)

    respond_to do |format|
      if @variation.save
        format.html { redirect_to variations_path, notice: 'Variation was successfully created.' }
        format.json { render :index, status: :created, location: @variation }
      else
        format.html { render :new }
        format.json { render json: @variation.errors, status: :unprocessable_entity }
      end
    end
  end

  # PATCH/PUT /variations/1
  # PATCH/PUT /variations/1.json
  def update
    respond_to do |format|
      if @variation.update(variation_params)
        format.html { redirect_to @variation, notice: 'Variation was successfully updated.' }
        format.json { render :show, status: :ok, location: @variation }
      else
        format.html { render :edit }
        format.json { render json: @variation.errors, status: :unprocessable_entity }
      end
    end
  end

  # DELETE /variations/1
  # DELETE /variations/1.json
  def destroy
    @variation.destroy
    respond_to do |format|
      format.html { redirect_to variations_url, notice: 'Variation was successfully destroyed.' }
      format.json { head :no_content }
    end
  end

  private
    # Use callbacks to share common setup or constraints between actions.
    def set_variation
      @variation = Variation.find(params[:id])
    end

    # Never trust parameters from the scary internet, only allow the white list through.
    def variation_params
      params.require(:variation).permit(:product_id, :size_id, :color_id, :quantity, :barcode)
    end
    def variation_import_params
      params.require(:variation_import).permit(:file)

    end
end

Na action new eu preciso pegar o resultado do join entre os modelos com suas descricoes e o codigo de barras e passar isso pro js via json