has_versions

has_versions is a simple plugin to version ActiveRecord objects. The versioned data is saved using Marshal. You can specify what attributes are going to be versioned and if versioning is automatically or not.

Installation

1) Install the plugin with script/plugin install git://github.com/fnando/has_versions.git

2) Generate a migration with script/generate migration create_versions and add the following code:

class CreateVersions < ActiveRecord::Migration
  def self.up
    create_table :versions do |t|
      t.references :versionable, :polymorphic => true
      t.references :user
      t.binary :data
      t.datetime :created_at
      t.integer :version, :default => 0, :null => false
    end

    add_index :versions, :versionable_type
    add_index :versions, :versionable_id
    add_index :versions, :user_id
    add_index :versions, :version
  end

  def self.down
    drop_table :versions
  end
end

3) Add the column version to all models you want to be versioned; first create the migration:

script/generate migration add_version_support_to_posts

Then add the following code:

class AddVersionSupportToPosts < ActiveRecord::Migration
  def self.up
    change_table :posts do |t|
      t.integer :version, :default => 0, :null => false
    end
  end

  def self.down
    remove_column :posts, :version
  end
end

3) Run the migrations with rake db:migrate

Usage

1) Add the association to your User model

class User < ActiveRecord::Base
  has_many :versions, :dependent => :nullify
end

2) Add the method call has_comments to your model.

class Post < ActiveRecord::Base
  has_versions
end

post = Post.first
user = User.first

# create the version only if any versioned attribute
# has changed
post.create_version

# create a version anyway!
post.create_version!

# retrieve current version number
post.version

# retrieve current version object
post.versions.current

# retrieve version #3
post.versions.get(3)

# retrive version #3 and
# raise SimplesIdeias::Versions::Exception::VersionNotFound
# if not found

# revert to a specific version,
# returning nil if version is not found
post.versions.revert_to(1)

# revert to a specific version and
# raise SimplesIdeias::Versions::Exception::VersionNotFound 
# if version is not found
post.versions.revert_to!(100)

# save an object without creating a version
post.save_without_version # => same as post.save
post.save_without_version(false) # => same as post.save(false)
post.save_without_version! # => post.save!

# set the user that created the version
post.version_author = user

# retrieve version author
post.version_author

# return true if version number >= 1
post.versioned?

# return true if current saving process
# is not meant to create a version
post.save_without_version?

# list of versioned attributes
post.versioned_attributes   

# you can control weither to create a version or not by
# overriding the method `create_version?`
class Post < ActiveRecord::Base
  has_versions

  def create_version?
    false
  end
end

# other possible options
has_versions :attributes => :all
has_versions :attributes => :content
has_versions :attributes => %w(content excerpt)
has_versions :auto => false
has_versions :except => :formatted_content

What about displaying a diff from two different versions? Well, you can use the helper method diff.

<%= diff @newer.data['content'], @newer.data['content'] %>

Use this CSS to display some formatted text:

.diff ins {
    background: #baffa6;
    text-decoration: none;
}

.diff del {
    background: #f88;
    text-decoration: none;
}

NOTE: You should have an User model. Otherwise, this won't work!

To-Do

• Create view helpers to display formatted version diffs

Maintainer

• Nando Vieira (http://simplesideias.com.br)

License

(The MIT License)

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.