Render from model in rails

render_from_model.rb

class SomeModel < ActiveRecord::Base

...

  def render_pdf
    ac = ApplicationController.new                                                                                                                                                
    ac.instance_variable_set("@some_variable_needed_in_template", some_variable)                                                                                                                  
    pdf = ac.render_to_string(pdf: "the_pdf_filename", template: 'pdf_templates/filename')
  end
end