The best thing to happen since bottled water
Wait, wasn't that bottled_decorators?, or was it bottled_services?, I am starting to lose track. Anyway! bottled_observers are an easy-to-use solution, for the Observer / Subscribe-Publish pattern in ruby. all you need to worry about is adding your business logic, let bottled_observers handle the rest!
Add this line to your application's Gemfile:
And then execute:
Or install it yourself as:
$ gem install bottled_observers
bottled_observers has two main modules you need to be aware of; BottledObserver and BottledObservable.
This module should be included in your observer class, and that observer class
should only contain a single public method:
class SendPushNotification include BottledObserver # <-- just like this! def call # Some intense and awesome logic to notify the hell out of them users. end end
That is all there is to it, your observer is now ready to rock'n'roll.
This module is included in any class that should allow observers to subscribe to it.
class Product include BottledObservable # <-- and just like this! # The rest of the class.... end
And that is it, your whole bottled_observers subscribe/publish cycle is ready to go.
The Subscribe / Publish Cycle
There are three main methods available in your arsenal that you need to be aware of:
These are available to your observable class instances, so if we wanted to subscribe
SendPushNotification observer to an instance of our
Product class, we could
do the following:
@product = Product.find(1) # <-- instantiate Product from a record in the database. @product.add_subscription SendPushNotification # <-- add a subscription for the SendPushNotification class
We now have a
SendPushNotification observer lying in wait for any publications from the
Then, when we want to notify the observer(s) of any changes to the instance, just set the state of the instance as modified using the
#modified method, and publish
this change of state to its subscribers:
Example case: sending push notifications after a successful save of the @product instance.
# The product is only in a modified state if the save is successful @product.modified if @product.save # If the @product's state is 'modified' the observers call method will be excecuted. # If the state is not modified, nothing will happen. @product.publish
Another thing that needs to be noted is, after publishing, the instances modified state is reset, so to publish anything again, it must be set again.
@product.modified @product.publish # <-- push notifications sent. @product.publish # <-- push notifications not sent.
@product.modified @product.publish # <-- push notifications sent. @product.modified @product.publish # <-- push notifications sent.
You can have as many observers subscribed to a single instance as you like:
@product.add_subscription SendPushNotification @product.add_subscription MailToMailingList @product.add_subscription CreateRecentActivityRecord @product.modified if @product.save @product.publish
#subscriptions will return an array of current observer instances subscribed to the observable instance:
@product.add_subscription SendPushNotification @product.subscriptions #=> [#<SendPushNotification:0x00...>]
To remove observers of a particular class, use
@product.add_subscription SendPushNotification @product.subscriptions #=> [#<SendPushNotification:0x00...>] @product.remove_subscription SendPushNotification @product.subscriptions #=> 
#remove_subscriptions (notice the plural) to, you guessed it, remove all observers:
@product.add_subscription SendPushNotification @product.add_subscription MailToMailingList @product.add_subscription CreateRecentActivityRecord @product.subscriptions #=> [#<SendPushNotification:0x00...>, ...] @product.remove_subscriptions @product.subscriptions #=> 
You can also check if your product is in a modified state by checking if it is
@product.publishable? #=> false @product.modified @product.publishable? #=> true
After checking out the repo, run
bin/setup to install dependencies. Then, run
rspec to run the tests. You can also run
bin/console for an interactive prompt that will allow you to experiment.
To install this gem onto your local machine, run
bundle exec rake install. To release a new version, update the version number in
version.rb, and then run
bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the
.gem file to rubygems.org.
Bug reports and pull requests are welcome on GitHub at https://github.com/John-Hayes-Reed/bottled_observers. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.
The gem is available as open source under the terms of the MIT License.
Code of Conduct
Everyone interacting in the BottledObservers project’s codebases, issue trackers, chat rooms and mailing lists is expected to have a beer or two before and enjoy life. Oh yeah and apparently this too: code of conduct.