quick answer needed on dependancy

Dave Smith wrote:

<code>
  mailinglist = Mailinglist.mail_template_mailinglists.find(:all,
:conditions => ["mail_template_id = ?", params[:id]])

    if mailinglist.empty?
      MailTemplate.find(params[:id]).destroy
    else
      flash[:notice] = 'Cannot delete mail template, as it is being used
by one or more mailinglist.'
    end
</code>

NoMethodError in Admin/mail templatesController#destroy

undefined method `mail_template_mailinglists' for #<Class:0x3333814>

any ideas anyone?