Rails%203%20In%20Action

316 CHAPTER 12 Sending email
Let’s now create a new folder at app/observers so that you can also reduce clutter
in the app/models folder. All the files inside the app directory are added to the load
path, so they will be require’able by your application. Inside the app/observers folder
you create a new file called comment_observer.rb that will hold the code for the observant
observer. In this file, put this:
class CommentObserver < ActiveRecord::Observer
def after_create(comment)
(comment.ticket.watchers - [comment.user]).each do |user|
Notifier.comment_updated(comment, user).deliver
end
end
end
This defines the observer that watches the Comment model and defines a method that
will be called after a new Comment is saved to the database, more commonly known as
the after_create callback.
At the top of the after_create method, you get the list of watchers for a ticket and
remove the user who has just made the comment from that list, because they
shouldn’t receive an email for a comment they just created!
The Notifier referenced inside the after_create is something you’ll create in a
little while. Consider it similar to an Active Record object, but for handling emails
instead. The comment_updated method will build an email for each of the users watching
this ticket, and deliver will send it out.
There’s a little bit of configuration you must do before this observer is used, however.
You must open config/application.rb and put this line inside the Ticketee
::Application class definition:
config.active_record.observers = :comment_observer
By calling this method, you are telling Rails to load the CommentObserver class, which
it will find without your help, because Rails will infer the name of the observer from the
symbol passed in. When you run bin/cucumber features/ticket_notifications
.feature, you’re told this:
And I press "Create Comment"
undefined method `watchers' for # (NoMethodError)
In this after_create method in your observer, you’re calling the watchers method to
get at the watchers for this ticket. It’s failing because you haven’t defined this association
yet, so let’s go ahead and do that now.
12.1.3 Defining the watchers association
The watchers method should return a collection of users who are watching a ticket,
including (by default) the user who has created the ticket in the first place, so that in
your feature alice@ticketee.com receives the email triggered by bob@ticketee.com’s
comment.