Userstamp Plugin (v 2.0)

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 by adding it to your Gemfile:

gem 'userstamp', :git => "https://github.com/coupa/userstamp.git", branch: 'master'

and run bundle install to install the new dependency.

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

Usage

In this new version of the Userstamp plug-in, the assumption is that you have two different categories of objects; those that manipulate, 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 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
end

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

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:

rake

Credits and Special Thanks

The original idea for this plugin came from the Rails Wiki article entitled "Extending ActiveRecord" on the Rails Wiki (no longer published).