ruby on rails - NoMethodError in PaymentsController#summary, undefined method `empty?' for nil:NilClass -

am getting following error:

nomethoderror in paymentscontroller#summary

undefined method `empty?' nil:nilclass extracted source (around line #134):

132    format.pdf 133    pdf = summarypdf.new(@klasses) 134    send_data pdf.render, filename: "payments summary_#{academicterm.current.details}.pdf", type: "application/pdf" 135   end 136 end 137end 

summarypdf class responsible printing income summary of payments in school. defined under payments controller as

def summary   @klasses = klass.all   respond_to |format|     format.html {render "summary"}     format.pdf       pdf = summarypdf.new(@klasses)       send_data pdf.render, filename: "payments summary_#{academicterm.current.details}.pdf", type: "application/pdf"     end   end end 

routes.rb

resources :payments   'search_form', :on=>:collection   'klass_menu',:on =>:collection   'byklass',:on =>:collection   'enrolment',:on =>:collection   'bystudent',:on =>:collection   'with_balance', :on=>:collection   'fully_paid', :on=>:collection   'all_with_balance', :on=>:collection   'all_fully_paid', :on=>:collection   'summary', :on=>:collection 

so, can me solution?

don't know render method on line 134 sure can call on unsaved summarypdf object? i'd render method needs saved instance of it.