I went through Chapter 13: Task H: Sending Mail of Agile Web Development with Rails today and stumbled upon an error.
This is error that I got when testing the order email send out functionality.
NameError (uninitialized constant OrdersController::Notifier):
app/controllers/orders_controller.rb:68:in `block in create'
app/controllers/orders_controller.rb:57:in `create'
The supposedly offending code is this:
Notifier.order_received(@order).deliver
After some futile investigation attempts - I restarted Rails and it worked!