Using barcode-generator's 'barcode' method in the model

Hi,

I am using matisimitsu's barcode-generator for barcodes in PDFs with
Prawn and Prawnto. http://github.com/matsimitsu/barcode-generator/tree/master.

I want to use the barcode method in a model where i generate the PDF
as a mail attachment, so that I can do this

def with_attachment(pdfFile, customer)
    subject "Voucher"
    recipients customer.email
    from "<xxx@yyy.com>"

    part :content_type => "text/html",
      :body => render_message("with_attachment", :customer =>
customer)

    attachment :content_disposition => "attachment",
        :body => pdfFile,
        :content_type => "application/pdf",
        :filename => 'voucher.pdf'
  end

Mailer.deliver_with_attachment(customer.generate_pdf_voucher,
customer)

Where generate_pdf_voucher is a method in the Customer model and
renders a PDF Document.

But right now, im getting the following error

NoMethodError: undefined method `barcode' for #<Customer:0x23fcf94>

How can I get around this problem? barcode_generator extends
ActionView to add the barcode method.

For now, I've copied the code into the Customer model and required the
imagemagick_wrapper in the model to get this to work. It works fine
but is there no cleaner way?