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2d74ed49f4
Signed-off-by: José Valim <jose.valim@gmail.com>
217 lines
6.7 KiB
Ruby
217 lines
6.7 KiB
Ruby
require 'singleton'
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require 'active_support/core_ext/array/wrap'
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require 'active_support/core_ext/module/aliasing'
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require 'active_support/core_ext/module/remove_method'
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require 'active_support/core_ext/string/inflections'
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module ActiveModel
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module Observing
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extend ActiveSupport::Concern
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module ClassMethods
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# == Active Model Observers Activation
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#
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# Activates the observers assigned. Examples:
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#
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# # Calls PersonObserver.instance
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# ActiveRecord::Base.observers = :person_observer
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#
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# # Calls Cacher.instance and GarbageCollector.instance
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# ActiveRecord::Base.observers = :cacher, :garbage_collector
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#
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# # Same as above, just using explicit class references
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# ActiveRecord::Base.observers = Cacher, GarbageCollector
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#
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# Note: Setting this does not instantiate the observers yet.
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# +instantiate_observers+ is called during startup, and before
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# each development request.
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def observers=(*values)
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@observers = values.flatten
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end
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# Gets the current observers.
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def observers
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@observers ||= []
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end
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# Gets the current observer instances.
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def observer_instances
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@observer_instances ||= []
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end
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# Instantiate the global Active Record observers.
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def instantiate_observers
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observers.each { |o| instantiate_observer(o) }
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end
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def add_observer(observer)
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unless observer.respond_to? :update
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raise ArgumentError, "observer needs to respond to `update'"
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end
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observer_instances << observer
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end
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def notify_observers(*arg)
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for observer in observer_instances
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observer.update(*arg)
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end
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end
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def count_observers
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observer_instances.size
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end
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protected
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def instantiate_observer(observer) #:nodoc:
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# string/symbol
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if observer.respond_to?(:to_sym)
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observer = observer.to_s.camelize.constantize.instance
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elsif observer.respond_to?(:instance)
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observer.instance
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else
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raise ArgumentError, "#{observer} must be a lowercase, underscored class name (or an instance of the class itself) responding to the instance method. Example: Person.observers = :big_brother # calls BigBrother.instance"
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end
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end
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# Notify observers when the observed class is subclassed.
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def inherited(subclass)
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super
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notify_observers :observed_class_inherited, subclass
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end
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end
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private
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# Fires notifications to model's observers
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#
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# def save
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# notify_observers(:before_save)
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# ...
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# notify_observers(:after_save)
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# end
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def notify_observers(method)
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self.class.notify_observers(method, self)
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end
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end
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# == Active Model Observers
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#
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# Observer classes respond to life cycle callbacks to implement trigger-like
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# behavior outside the original class. This is a great way to reduce the
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# clutter that normally comes when the model class is burdened with
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# functionality that doesn't pertain to the core responsibility of the
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# class. Example:
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#
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# class CommentObserver < ActiveModel::Observer
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# def after_save(comment)
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# Notifications.deliver_comment("admin@do.com", "New comment was posted", comment)
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# end
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# end
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#
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# This Observer sends an email when a Comment#save is finished.
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#
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# class ContactObserver < ActiveModel::Observer
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# def after_create(contact)
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# contact.logger.info('New contact added!')
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# end
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#
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# def after_destroy(contact)
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# contact.logger.warn("Contact with an id of #{contact.id} was destroyed!")
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# end
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# end
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#
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# This Observer uses logger to log when specific callbacks are triggered.
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#
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# == Observing a class that can't be inferred
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#
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# Observers will by default be mapped to the class with which they share a
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# name. So CommentObserver will be tied to observing Comment, ProductManagerObserver
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# to ProductManager, and so on. If you want to name your observer differently than
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# the class you're interested in observing, you can use the Observer.observe class
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# method which takes either the concrete class (Product) or a symbol for that
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# class (:product):
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#
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# class AuditObserver < ActiveModel::Observer
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# observe :account
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#
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# def after_update(account)
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# AuditTrail.new(account, "UPDATED")
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# end
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# end
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#
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# If the audit observer needs to watch more than one kind of object, this can be
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# specified with multiple arguments:
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#
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# class AuditObserver < ActiveModel::Observer
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# observe :account, :balance
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#
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# def after_update(record)
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# AuditTrail.new(record, "UPDATED")
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# end
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# end
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#
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# The AuditObserver will now act on both updates to Account and Balance by treating
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# them both as records.
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#
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class Observer
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include Singleton
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class << self
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# Attaches the observer to the supplied model classes.
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def observe(*models)
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models.flatten!
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models.collect! { |model| model.respond_to?(:to_sym) ? model.to_s.camelize.constantize : model }
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remove_possible_method(:observed_classes)
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define_method(:observed_classes) { models }
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end
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# Returns an array of Classes to observe.
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#
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# You can override this instead of using the +observe+ helper.
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#
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# class AuditObserver < ActiveModel::Observer
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# def self.observed_classes
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# [Account, Balance]
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# end
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# end
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def observed_classes
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Array.wrap(observed_class)
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end
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# The class observed by default is inferred from the observer's class name:
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# assert_equal Person, PersonObserver.observed_class
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def observed_class
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if observed_class_name = name[/(.*)Observer/, 1]
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observed_class_name.constantize
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else
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nil
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end
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end
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end
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# Start observing the declared classes and their subclasses.
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def initialize
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observed_classes.each { |klass| add_observer!(klass) }
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end
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def observed_classes #:nodoc:
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self.class.observed_classes
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end
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# Send observed_method(object) if the method exists.
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def update(observed_method, object) #:nodoc:
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send(observed_method, object) if respond_to?(observed_method)
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end
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# Special method sent by the observed class when it is inherited.
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# Passes the new subclass.
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def observed_class_inherited(subclass) #:nodoc:
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self.class.observe(observed_classes + [subclass])
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add_observer!(subclass)
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end
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protected
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def add_observer!(klass) #:nodoc:
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klass.add_observer(self)
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end
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end
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end
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