Class: ActiveSupport::Subscriber
Relationships & Source Files | |
Extension / Inclusion / Inheritance Descendants | |
Subclasses:
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Inherits: | Object |
Defined in: | activesupport/lib/active_support/subscriber.rb |
Overview
Subscriber
is an object set to consume Notifications
. The subscriber dispatches notifications to a registered object based on its given namespace.
An example would be an Active Record subscriber responsible for collecting statistics about queries:
module ActiveRecord
class StatsSubscriber < ActiveSupport::Subscriber
attach_to :active_record
def sql(event)
Statsd.timing("sql.#{event.payload[:name]}", event.duration)
end
end
end
After configured, whenever a "sql.active_record"
notification is published, it will properly dispatch the event (ActiveSupport::Notifications::Event) to the sql
method.
We can detach a subscriber as well:
ActiveRecord::StatsSubscriber.detach_from(:active_record)
Class Method Summary
-
.attach_to(namespace, subscriber = new, notifier = ActiveSupport::Notifications, inherit_all: false)
Attach the subscriber to a namespace.
-
.detach_from(namespace, notifier = ActiveSupport::Notifications)
Detach the subscriber from a namespace.
-
.method_added(event)
Adds event subscribers for all new methods added to the class.
- .new ⇒ Subscriber constructor
- .subscribers
- .add_event_subscriber(event) private
- .remove_event_subscriber(event) private
Instance Method Summary
Constructor Details
.new ⇒ Subscriber
# File 'activesupport/lib/active_support/subscriber.rb', line 130
def initialize @patterns = {} super end
Class Method Details
.add_event_subscriber(event) (private)
[ GitHub ]# File 'activesupport/lib/active_support/subscriber.rb', line 85
def add_event_subscriber(event) # :doc: return if invalid_event?(event) pattern = prepare_pattern(event) # Don't add multiple subscribers (e.g. if methods are redefined). return if pattern_subscribed?(pattern) subscriber.patterns[pattern] = notifier.subscribe(pattern, subscriber) end
.attach_to(namespace, subscriber = new, notifier = ActiveSupport::Notifications, inherit_all: false)
Attach the subscriber to a namespace.
# File 'activesupport/lib/active_support/subscriber.rb', line 35
def attach_to(namespace, subscriber = new, notifier = ActiveSupport::Notifications, inherit_all: false) @namespace = namespace @subscriber = subscriber @notifier = notifier @inherit_all = inherit_all subscribers << subscriber # Add event subscribers for all existing methods on the class. fetch_public_methods(subscriber, inherit_all).each do |event| add_event_subscriber(event) end end
.detach_from(namespace, notifier = ActiveSupport::Notifications)
Detach the subscriber from a namespace.
# File 'activesupport/lib/active_support/subscriber.rb', line 50
def detach_from(namespace, notifier = ActiveSupport::Notifications) @namespace = namespace @subscriber = find_attached_subscriber @notifier = notifier return unless subscriber subscribers.delete(subscriber) # Remove event subscribers of all existing methods on the class. fetch_public_methods(subscriber, true).each do |event| remove_event_subscriber(event) end # Reset notifier so that event subscribers will not add for new methods added to the class. @notifier = nil end
.method_added(event)
Adds event subscribers for all new methods added to the class.
# File 'activesupport/lib/active_support/subscriber.rb', line 69
def method_added(event) # Only public methods are added as subscribers, and only if a notifier # has been set up. This means that subscribers will only be set up for # classes that call #attach_to. if public_method_defined?(event) && notifier add_event_subscriber(event) end end
.remove_event_subscriber(event) (private)
[ GitHub ]# File 'activesupport/lib/active_support/subscriber.rb', line 96
def remove_event_subscriber(event) # :doc: return if invalid_event?(event) pattern = prepare_pattern(event) return unless pattern_subscribed?(pattern) notifier.unsubscribe(subscriber.patterns[pattern]) subscriber.patterns.delete(pattern) end
.subscribers
[ GitHub ]# File 'activesupport/lib/active_support/subscriber.rb', line 78
def subscribers @@subscribers ||= [] end
Instance Method Details
#call(event)
[ GitHub ]# File 'activesupport/lib/active_support/subscriber.rb', line 135
def call(event) method = event.name[0, event.name.index(".")] send(method, event) end