scaffold return to index page

i am using rubyonrails 2.1 and i have used scaffold .on controller i added new method and html.erb now what i want is to back to the index.html.erb page of the scaffold ,i have tried to use render but on the original scaffold i have met the problem on the below "You have a nil object when you didn't expect it! You might have expected an instance of Array. The error occurred while evaluating nil.each" can any one tell me what should i do thanks.

you must use redirect_to, render :action only display the action it does not execute the method