Overview

The Userstamp Plugin extends ActiveRecord::Base to add automatic updating of ‘creator’, ‘updater’, and ‘deleter’ attributes. It is based loosely on the ActiveRecord::Timestamp module.

Two class methods (model_stamper and stampable) are implemented in this plugin. The model_stamper method is used in models that are responsible for creating, updating, or deleting other objects. The stampable method is used in models that are subject to being created, updated, or deleted by ‘stampers’.

Installation

Installation of the plugin can be done using the built in Rails plugin script. Issue the following command from the root of your application:

  script/plugin install git://github.com/delynn/userstamp.git

Once installed you will need to restart your application for the plugin to be loaded into the Rails environment.

You might also be interested in using Piston[http://piston.rubyforge.org/index.html] to manage the importing and future updating of this plugin.

Usage

In this new version of the Userstamp plug-in, the assumption is that you have two different categories of objects; those that mani˝pulate, and those that are manipulated. For those objects that are being manipulated there’s the Stampable module and for the manipulators there’s the Stamper module. There’s also the actual Userstamp module for your controllers that assists in setting up your environment on a per request basis.

To better understand how all this works, I think an example is in order. For this example we will assume that a weblog application is comprised of User and Post objects. The first thing we need to do is create the migrations for these objects, and the plug-in gives you a userstamps method for very easily doing this:

  class CreateUsers < ActiveRecord::Migration
    def self.up
      create_table :users, :force => true do |t|
        t.timestamps
        t.userstamps
        t.name
      end
    end

    def self.down
      drop_table :users
    end
  end

  class CreatePosts < ActiveRecord::Migration
    def self.up
      create_table :posts, :force => true do |t|
        t.timestamps
        t.userstamps
        t.title
      end
    end

    def self.down
      drop_table :posts
    end
  end

Second, since Users are going to manipulate other objects in our project, we’ll use the model_stamper method in our User class:

  class User < ActiveRecord::Base
    model_stamper
  end

Finally, we need to setup a controller to set the current user of the application. It’s recommended that you do this in your ApplicationController:

  class ApplicationController < ActionController::Base
    include Userstamp
  end

If all you are interested in is making sure all tables that have the proper columns are stamped by the currently logged in user you can stop right here. More than likely you want all your associations setup on your stamped objects, and that’s where the stampable class method comes in. So in our example we’ll want to use this method in both our User and Post classes:

  class User < ActiveRecord::Base
    model_stamper
    stampable
  end

  class Post < ActiveRecord::Base
    stampable
  end

Okay, so what all have we done? The model_stamper class method injects two methods into the User class. They are #stamper= and #stamper and look like this:

  def stamper=(object)
    object_stamper = if object.is_a?(ActiveRecord::Base)
      object.send("#{object.class.primary_key}".to_sym)
    else
      object
    end

    Thread.current["#{self.to_s.downcase}_#{self.object_id}_stamper"] = object_stamper
  end

  def stamper
    Thread.current["#{self.to_s.downcase}_#{self.object_id}_stamper"]
  end

The big change with this new version is that we are now using Thread.current to save the current stamper so as to avoid conflict with concurrent requests.

The stampable method allows you to customize what columns will get stamped, and also creates the creator, updater, and deleter associations.

The Userstamp module that we included into our ApplicationController uses the setter method to set which user is currently making the request. By default the ‘set_stampers’ method works perfectly with the RestfulAuthentication[http://svn.techno-weenie.net/projects/plugins/restful_authentication] plug-in:

  def set_stampers
    User.stamper = self.current_user
  end

If you aren’t using ActsAsAuthenticated, then you need to create your own version of the set_stampers method in the controller where you’ve included the Userstamp module.

Now, let’s get back to the Stampable module (since it really is the interesting one). The Stampable module sets up before_* filters that are responsible for setting those attributes at the appropriate times. It also creates the belongs_to relationships for you.

If you need to customize the columns that are stamped, the stampable method can be completely customized. Here’s an quick example:

  class Post < ActiveRecord::Base
    acts_as_stampable :stamper_class_name => :person,
                      :creator_attribute  => :create_user,
                      :updater_attribute  => :update_user,
                      :deleter_attribute  => :delete_user
  end

If you are upgrading your application from the old version of Userstamp, there is a compatibility mode to have the plug-in use the old "_by" columns by default. To enable this mode, add the following line to the RAILS_ROOT/config/environment.rb file:

  Ddb::Userstamp.compatibility_mode = true

If you are having a difficult time getting the Userstamp plug-in to work, I recommend you checkout the sample application that I created. You can find this application on GitHub[http://github.com/delynn/userstamp_sample]

Uninstall

Uninstalling the plugin can be done using the built in Rails plugin script. Issue the following command from the root of your application:

  script/plugin remove userstamp

Documentation

RDoc has been run on the plugin directory and is available in the doc directory.

Running Unit Tests

There are extensive unit tests in the "test" directory of the plugin. These test can be run individually by executing the following command from the userstamp directory:

 ruby test/compatibility_stamping_test.rb
 ruby test/stamping_test.rb
 ruby test/userstamp_controller_test.rb

Bugs & Feedback

Bug reports and feedback are welcome via my delynn+userstamp@gmail.com email address. I also encouraged everyone to clone the git repository and make modifications—I’ll be more than happy to merge any changes from other people’s branches that would be beneficial to the whole project.

Credits and Special Thanks

The original idea for this plugin came from the Rails Wiki article entitled {Extending ActiveRecord}[http://wiki.rubyonrails.com/rails/pages/ExtendingActiveRecordExample].