EnlightenedObservers

This plugin makes it quick and easy to share the controller information with observers, including session information. This is useful when observers need to report the current_user that made a certain action happen.

A sizable amount of the code and idea for this plugin comes from:
Garry Dolley’s Let ActiveRecord Observers see controller context

Usage

class MyController < ActionController::Base
  include EnlightenedObservers
  enlighten_observer :my_observer
  ...
end

In your observers, also include EnlightenedObservers::Enlightenment:

class MyObserver < ActiveRecord::Observer
  include EnlightenedObservers::Enlightenment
  ...
end

Of course, you still have to initialize any observer the normal way in config/environment.rb

  config.active_record.observers = :my_observer

Now, in your observers, you can access data saved by calling controller – but be sure to check if controller.nil?

To get data stored that you specified in the hash at the end of the enlighten_observer declaration, simply access it as a hash: controller, and that will yield the computed value of self.send(:controller_method_to_call) where self is the controller instance.

Installation

To enable the library your Rails 2.1 (or greater) project, use the gem configuration method in “config/environment.rb”

Rails::Initializer.run do |config|
  config.gem 'moorage-enlightened_observers', :lib => 'enlightened_observers', :source => 'http://gems.github.com'
end

The :lib is important, because rails gets confused when the name of the gem is different from the library.

And of course, run

  rake gems:install

To get them installed on your system.

Optionally, to unpack it into your application, just run:

  rake gems:unpack GEM=moorage-enlightened_observers

Example

A controller:

  class OrganizationsController < ApplicationController

    include EnlightenedObservers

    enlighten_observer :alert_event_observer

    before_filter :authorization_required, :only => [:edit, :update, :destroy]

def edit
…
end
end

An observer:

  class AlertEventObserver < ActiveRecord::Observer
    include EnlightenedObservers::Enlightenment
    observe :organization

    def after_update(alertable)
      f = Alert.new
      unless controller.nil?
        ... # do somehting
      end
      f.title = "created #{alertable.name}"
      f.save
    end
  end

How it Works

By adding include EnlightenedObservers::Enlightenment to your Observer, an attr_accessor for controller is added, which you can access any time from your Observer. Depending on how your oberserver has been called, this variable might have been set, with the controller that was used to access and change the model this observer has been observing.

By calling enlighten_observer :my_observer in your controller, you’re adding an around_filter to the controller that sets and unsets the observers’ controller accessor. Each time a controller action is called, this around filter finds the currently running instance of the observer (using code copied from module ActiveModel::Observing::ClassMethods).

NOTE: we could have had the enlighten_observer call actually do the include EnlightenedObservers::Enlightenment in the Observer – however, since your observer can be run even if the model was changed through something OTHER than a controller action, we chose to decouple the two calls.

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Copyright © 2008 ThriveSmart, LLC, based on code by Garry Dolley, released under the MIT license.