version_fu is a ActveRecord versioning plugin that that is based on the dirty attribute checking introduced in Rails 2.1. It has been updated for compatibility with Rails 3.

gem install version_fu

If you’re using Rails 3, add it to your Gemfile

gem 'version_fu'

Let’s say I have a pages table:

class Page < ActiveRecord::Base
  # attributes: id, type, title, body, created_at, updated_at, creator_id, author_id
end

I want to track any changes made. First step will be to make a new page_versions table:

class CreatePageVersions < ActiveRecord::Migration
  def self.up
    create_table :page_versions do |t|
      t.integer :page_id, :version, :author_id
      t.string  :title
      t.text    :body
      t.timestamps
    end
  end

  def self.down
    drop_table :page_versions
  end
end

In this case, the author_id column represents the last person to edit the page. We want to track this attribute with every version. However, the creator_id is the person who created the page. The will never change, so it’s not part of the versioned table.

Don’t forget to add a version column to your pages table. Have it default to 1 just to be safe (although the plugin should account for this):

class AddVersionToPages < ActiveRecord::Migration
  def self.up
    add_column :pages, :version, :integer, :default=>1
  end
  def self.down
    remove_column :pages, :version
  end
end

Of course if you’re adding this plugin to a table with existing data, you’ll probably want to instantiate some initial versions to start with.

Alright, so now that the database tables are in place, we can fire up version_fu. It’s quite simple:

class Page < ActiveRecord::Base
  version_fu
end

Thats it.

You can pass a few configuration options if need be. If you stick with the defaults above, you can skip all this.

class Page < ActiveRecord::Base
  version_fu :class_name=>'Version', :foreign_key=>'page_id', :table_name=>'page_versions', :version_column=>'version'
end

• :class_name - The name of the versioned class. It will be a submodule of the versioning class - e.g. Page::Version

• :foreign_key - The column in the versioned table associated with the versioning class

• :table_name - The name of the versioned table

• :version_column - The name of the version column

Now that you’ve got some versions, it would be nice to use ActiveRecord associations on it. For example, Page.first.versions.latest.author wouldn’t currently work because the Page::Version class doesn’t know about the author method. The version_fu call does all you to pass a block which is executed by the versioned class. There is just one gotcha for associations:

class Page < ActiveRecord::Base
  version_fu do
    belongs_to :author, :class_name=>'::Author'
  end
end

Don’t forget the class name, or you’ll get a warning

By default a new version will be saved whenever a versioned column is changed. However, you can control this at a more fine grained level. Just override the create_new_version? method. For example, let’s say you only want to save a new version if both the page title and body changed. Taking advantage of the dirty attribute methods, you could do something like this:

class Page < ActiveRecord::Base
  version_fu do
    belongs_to :author, :class_name=>'::Author'
  end
  def create_new_version?
    title_changed? && body_changed?
  end
end

• version_fu was created by Jordan McKible jordan.mckible.com

• Available on GitHub at github.com/jmckible/version_fu

• Available on RubyGems.org at rubygems.org/gems/version_fu

• acts_as_versioned by Rick Olson github.com/technoweenie/acts_as_versioned/tree/master