Rails%203%20In%20Action

Sending ticket notifications
Here you must do two things: define the watchers association and add the ticket
owner to the watchers list when the ticket is created.
You use another has_and_belongs_to_many association to define the watchers
collection, this time in your Ticket model. To define it, put this code inside the
Ticket model, along with the other has_and_belongs_to_many for tags:
has_and_belongs_to_many :watchers, :join_table => "ticket_watchers",
:class_name => "User"
Here you pass the :join_table option to specify a custom table name for your
has_and_belongs_to_many. If you didn’t do this, then the table name would be
inferred by Rails to be ticket_users, which doesn’t really explain the purpose of this
table as much as ticket_watchers does. You pass another option too, :class_name,
which tells your model that the objects from this association are User objects. If you
left this option out, Active Record would imply that you wanted the Watcher class
instead, which doesn’t exist.
You can create a migration that can be used to create this table by using this
command:
rails g migration create_ticket_watchers_table
Unfortunately, the migration won’t read your mind in this instance, so you need to
open it and change it to resemble the following listing.
Listing 12.2 db/migrate/[timestamp]_create_ticket_watchers_table.rb
class CreateTicketWatchersTable < ActiveRecord::Migration
def change
create_table :ticket_watchers, :id => false do |t|
t.integer :user_id, :ticket_id
end
end
end
Remember: you need to specify the id option here so that your join table doesn’t have
a primary key.
Let’s save and then run this file using rake db:migrate, and let’s not forget to run
rake db:test:prepare either.
Now that you have your watchers method defined, you need to add the user who
creates a ticket to the list of watchers for that ticket. You can do this by using an
after_create callback on your Ticket model like this:
after_create :creator_watches_me
To define the creator_watches_me method, you put the following code at the bottom
of the Ticket class definition:
private
def creator_watches_me
self.watchers