How many times have you seen this in a rails app?
class User after_create :deliver_welcome_message protected def deliver_welcome_message Notifier.deliver_welcome_message(self) end end
Why is the user concerned with the delivery of his own welcome message? It seems like the Notifier should be responsible for that.
Observational makes it possible to make it the Notifier's responsibility, using the observer pattern.
The equivalent of the above example is:
class Notifier < ActionMailer::Base observes :user, :invokes => :deliver_welcome_message, :after => :create def welcome_message(user) # do mailer stuff here end end
After a user is created, Notifier.deliver_welcome_message(that_user) will be invoked.
It's also possible to specify that the observer method gets called with a specific attribute from the observed object.
class Creditor observes :message, :invokes => :use_credit, :with => :creator, :after => :create def use_credit(user) # do something end end
After a message is created, Creditor.use_credit(message.creator) will be called.
Observational supports all of ActiveRecord's callbacks.
Observational uses YARD, because it's a million times better than RDoc. You can find the docs at docs.github.com/giraffesoft/observational
General Purpose Observers
Observational can also be used to add observers to ruby classes that aren't related to active_record. But, that's not documented yet :-).
Copyright © 2009 James Golick. See LICENSE for details.