Rails%203%20In%20Action

gem 'delayed_job'
Background workers
Then you’ll need to run bundle install to install it. Once you’re done there, you can
run this command, which will generate a migration to create the delayed_job table:
rails g delayed_job
You can now run this migration with rake db:migrate db:test:prepare. That’s all
that’s needed to set up the gem itself.
Your next task is to create a job. A job is any object that responds to perform. This
method needs to perform the action of sending out the email to all the watchers of
the ticket, which is currently the responsibility of the after_create method in
CommentObserver, which uses this code:
watchers = comment.ticket.watchers - [comment.user]
watchers.each do |user|
Notifier.comment_updated(comment, user).deliver
end
You’ll take this code out of the after_create method and replace it with code to
enqueue your job to be performed, using a method given to you by the delayed_job
gem:
Delayed::Job.enqueue CommentNotifierJob.new(comment.id)
The CommentNotifierJob class here will actually be a Struct object. You can create
the code by first creating a new directory called app/jobs and then a new file in it
called comment_notifier_job.rb, using the code you stole from the after_create
method as shown in the following listing.
Listing 16.6 app/jobs/comment_notifier_job.rb
class CommentNotifierJob < Struct.new(:comment_id)
def perform
comment = Comment.find(comment_id)
watchers = comment.ticket.watchers - [comment.user]
watchers.each do |user|
Notifier.comment_updated(comment, user).deliver
end
end
end
In the perform method here, you find the comment based on the comment_id and
then iterate through all the watchers of the comment’s ticket who are not the commenter
themselves, sending them each an email that the ticket has been updated with
a new comment.
By enqueueing this job using the Delayed::Job.enqueue method, the
delayed_job gem will store a marshalled format (actually a YAML string) of this object
in the table, such as this:
--- !ruby/struct:CommentNotifierJob \ncomment_id: 1\n
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