form.input :notes

<input name="job[shifts][shift_id][notes]" />

form.whatever :notes   # Returns "job[shifts][shift_id][notes]"

def dom_input_name(form, field_name)
  "#{form.object_name}[#{field_name.to_s.sub(/?$/,"")}]"
end

dom_input_name(form, :notes)