embedding barcode generated with barby gem into the prawn document

From my controller I create pdf:

def show
    @order = Order.find(params[:id])

    respond_to do |format|
      format.html # show.html.erb
      format.json { render json: @order }
      format.pdf do
        pdf = InvoicePdf.new(@order, view_context)

        send_data pdf.render, filename: "invoice_#{@order.order_number}.pdf",
                              type: "application/pdf",
                              disposition: "inline",
                              size: 10
      end
    end
  end

invoice_pdf.rb:

require 'barby'
require 'barby/barcode/code_39'
require 'barby/outputter/prawn_outputter'

class InvoicePdf < Prawn::Document
    def initialize(order, view)
        super({
            :top_margin => 70,
            :page_size => 'A4',
            :font_size => 10,
            :text  => 8
            })

        @order = order
        @view = view
        order_number
        barcode
    end

    def order_number
        text "Order #{@order.order_number}"
    end

    def barcode
        barcode = Barby::Code39.new @order.order_number
        barcode.annotate_pdf(XXXX)
    end
end

How should I modify my barcode method or the options marked as XXXX to embed barcode into PDF document?

EDIT

In your InvoicePdf class, change the barcode method to:

def barcode
  barcode = Barby::Code39.new @order.order_number
  barcode.annotate_pdf(self)
end

The annotate_pdf method takes a Prawn::Document as its argument, which is self here.

---

Original Answer

If you want to create a new pdf with your barcode, you can just do:

def barcode
  _barcode = Barby::Code39.new(@order.order_number)
  outputter = Barby::PrawnOutputter.new(_barcode)
  outputter.to_pdf
end

Note that you can specify pdf options (including height, margins, page size, etc.) on the new PrawnOutputter or on the to_pdf call. See the documentation for more details: https://github.com/toretore/barby/wiki/Outputters and http://rdoc.info/github/toretore/barby/Barby/PrawnOutputter.

And if you want to write it to a file do:

File.open("my_file.pdf","w") { |f| f.print barcode }

Note that you can also just call _barcode.to_pdf, which seems to have the same effect as creating a new PrawnOutputter, but this functionality is not described in the Barby documentation.

If you have an existing pdf document (as a Prawn::Document) that you want to write a barcode to, note that you could do:

def barcode(p_pdf)
  _barcode = Barby::Code39.new(@order.order_number)
  _barcode.annotate_pdf(p_pdf) 
end