ObjectPubSub
ObjectPubSub is an implementation of the Observer pattern for Ruby that provides finer-grained controll over message passing than does the Observable module from Ruby's stdlib. The including class can publish multiple event types, and the subscribers can specify both which event types to listen for and what method on the subscriber should be invoked for each event type.
Installation
Add this line to your application's Gemfile:
gem 'object_pub_sub'
And then execute:
$ bundle
Or install it yourself as:
$ gem install object_pub_sub
Usage
In the class that will be publishing events (the "Observable"), simply
include ObjectPubSub and then publish events where appropriate:
class UserValidator
include ObjectPubSub
attr_reader :user, :errors
def initialize(user)
@user = user
@errors = {}
end
def validate
validate_username #def exluded for brevity
validate_password #def exluded for brevity
validate_email #def exluded for brevity
notify_subscribers
end
private
def notify_subscribers
if errors.any?
publish_event(:invalid, errors)
else
publish_event(:valid, user)
end
end
end
Then, objects that care about those events can subscribe to them:
class ValidationLogger
def initialize(name, logger = nil)
@logger = logger || Logger.new(STDERR)
@name = name
end
def log_validation_error(errors)
logger.warn("Validation errors on #{name}: #{errors}")
end
end
class CreateUser
def initialize(logger = nil)
@logger = logger
end
def perform(user_attrs)
user = User.new(attrs)
validation_logger = ValidationLogger.new("User creation", logger)
validator = UserValidator.new(user)
validator.add_subscriber(self, :valid => :handle_valid_user, :invalid => :handle_invalid_user)
validator.add_subscriber(validation_logger, :invalid => :log_validation_error)
validator.validate
end
def handle_valid_user(user)
# ...
end
def handle_invalid_user(errors)
# ...
end
end
CreateUser.new \
.perform(:username => 'foo', :email => 'foo@example.com', :password => 'foopassword')
See the examples under /spec for more information.
Contributing
- Fork it
- Create your feature branch (
git checkout -b my-new-feature) - Commit your changes (
git commit -am 'Add some feature') - Push to the branch (
git push origin my-new-feature) - Create new Pull Request