ruby-on-rails-3.2 - ROR: 未定義のメソッド「authenticate」

Question

Rails アプリケーションに「パスワードの変更」機能を追加したいので、ここから調べます (207.44.138.58/~rorexper/viewtopic.php?t=690&highlight=&sid=16f7417dcbb3cb8960912c8134351fd9)。

ビューページに次を追加します：-

 = form_tag :action => 'update' do
   - flash.each do |key, value|
     %div.TxtRed{:class => "flash #{key}"}= value
   %p
     %label Current password
     %br
     = password_field_tag "user[current_password]", nil
   %p
     %label New password
     %br
     = password_field_tag "user[password]", nil
   %p
     %label Confirm password
     %br
     = password_field_tag "user[password_confirmation]", nil
   %P
     = button_tag "Save", :class => "btn-custom ML10", :type => :submit

そしてコントローラで： -

  def update
    return unless request.post?
    @user = Refinery::User.find_by_id(current_user.id)
    if current_user = Refinery::User.authenticate(@user.username, params[:user][:current_password])

       if (params[:user][:password] == params[:user][:password_confirmation])

          current_user.encrypted_password = crypted_password(params[:user] [:password] ,current_user.salt)

          flash[:notice] = current_user.save ?"Password changed" :"Password not changed"
          redirect_to my_page_path

       else

          flash[:notice] = "Password mismatch"
          @current_password = params[:current_password]

       end

    else

       flash[:notice] = "Wrong password"

    end
 end

 def crypted_password(password, salt)
   string_to_hash = password + "nyros" + salt
   Digest::SHA1.hexdigest(string_to_hash)
 end

しかし、それは正しく機能せず、エラーが発生します:「未定義のメソッド `authenticate' for #」