laserlemon/vestal_versions

= Vestal Versions

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Finally, DRY ActiveRecord versioning!

<tt>acts_as_versioned</tt>[http://github.com/technoweenie/acts_as_versioned] by technoweenie[http://github.com/technoweenie] was a great start, but it failed to keep up with ActiveRecord's introduction of dirty objects in version 2.1. Additionally, each versioned model needs its own versions table that duplicates most of the original table's columns. The versions table is then populated with records that often duplicate most of the original record's attributes. All in all, not very DRY.

<tt>vestal_versions</tt>[http://github.com/laserlemon/vestal_versions] requires only one versions table (polymorphically associated with its parent models) and no changes whatsoever to existing tables. But it goes one step DRYer by storing a serialized hash of _only_ the models' changes. Think modern version control systems. By traversing the record of changes, the models can be reverted to any point in time.

And that's just what <tt>vestal_versions</tt> does. Not only can a model be reverted to a previous version number but also to a date or time!

== Compatibility

Tested with Active Record 3.2.16 with Ruby 1.9.3 and 1.9.2.

== Installation

In the Gemfile:

** Note: I am giving this project some much needed love to keep her relevant in a post Rails 3 world. I will be finalizing a version to support 1.9.2+ and Rails 3.2+ soon and pushing the gem, till then, use the git repo:
~dreamr
  
  gem 'vestal_versions', :git => 'git://github.com/laserlemon/vestal_versions'
  

Next, generate and run the first and last versioning migration you'll ever need:

  $ rails generate vestal_versions:migration
  $ rake db:migrate

== Example

To version an ActiveRecord model, simply add <tt>versioned</tt> to your class like so:

  class User < ActiveRecord::Base
    versioned

    validates_presence_of :first_name, :last_name

    def name
      "#{first_name} #{last_name}"
    end
  end

It's that easy! Now watch it in action...

  >> u = User.create(:first_name => "Steve", :last_name => "Richert")
  => #<User first_name: "Steve", last_name: "Richert">
  >> u.version
  => 1
  >> u.update_attribute(:first_name, "Stephen")
  => true
  >> u.name
  => "Stephen Richert"
  >> u.version
  => 2
  >> u.revert_to(10.seconds.ago)
  => 1
  >> u.name
  => "Steve Richert"
  >> u.version
  => 1
  >> u.save
  => true
  >> u.version
  => 3
  >> u.update_attribute(:last_name, "Jobs")
  => true
  >> u.name
  => "Steve Jobs"
  >> u.version
  => 4
  >> u.revert_to!(2)
  => true
  >> u.name
  => "Stephen Richert"
  >> u.version
  => 5

== Upgrading to 1.0

For the most part, version 1.0 of <tt>vestal_versions</tt> is backwards compatible, with just a few notable changes:

* The versions table has been beefed up. You'll need to add the following columns (and indexes, if you feel so inclined):

    change_table :versions do |t|
      t.belongs_to :user, :polymorphic => true
      t.string :user_name
      t.string :tag
    end

    change_table :versions do |t|
      t.index [:user_id, :user_type]
      t.index :user_name
      t.index :tag
    end

* When a model is created (or updated the first time after being versioned), an initial version record with a number of 1 is no longer created. These aren't used during reversion and so they end up just being dead weight. Feel free to scrap all your versions where <tt>number == 1</tt> after the upgrade if you'd like to free up some room in your database (but you don't have to).

* Models that have no version records in the database will return a <tt>@user.version</tt> of 1. In the past, this would have returned <tt>nil</tt> instead.

* <tt>Version</tt> has moved to <tt>VestalVersions::Version</tt> to make way for custom version classes.

* <tt>Version#version</tt> did not survive the move to <tt>VestalVersions::Version#version</tt>. That alias was dropped (too confusing). Use <tt>VestalVersions::Version#number</tt>.

== New to 1.0

There are a handful of exciting new additions in version 1.0 of <tt>vestal_versions</tt>. A lot has changed in the code: much better documentation, more modular organization of features, and a more exhaustive test suite. But there are also a number of new features that are available in this release of <tt>vestal_versions</tt>:

* The ability to completely skip versioning within a new <tt>skip_version</tt> block:

    @user.version # => 1
    @user.skip_version do
      @user.update_attribute(:first_name, "Stephen")
      @user.first_name = "Steve"
      @user.save
      @user.update_attributes(:last_name => "Jobs")
    end
    @user.version # => 1

  Also available, are <tt>merge_version</tt> and <tt>append_version</tt> blocks. The <tt>merge_version</tt> block will compile the possibly multiple versions that would result from the updates inside the block into one summary version. The single resulting version is then tacked onto the version history as usual. The <tt>append_version</tt> block works similarly except that the resulting single version is combined with the most recent version in the history and saved.

* Version tagging. Any version can have a tag attached to it (must be unique within the scope of the versioned parent) and that tag can be used for reversion.

    @user.name # => "Steve Richert"
    @user.update_attribute(:last_name, "Jobs")
    @user.name # => "Steve Jobs"
    @user.tag_version("apple")
    @user.update_attribute(:last_name, "Richert")
    @user.name # => "Steve Richert"
    @user.revert_to("apple")
    @user.name # => "Steve Jobs"

  So if you're not big on version numbers, you could just tag your versions and avoid the numbers altogether.

* Resetting. This is basically a hard revert. The new <tt>reset_to!</tt> instance method behaves just like the <tt>revert_to!</tt> method except that after the reversion, it will also scrap all the versions that came after that target version.

    @user.name # => "Steve Richert"
    @user.version # => 1
    @user.versions.count # => 0
    @user.update_attribute(:last_name, "Jobs")
    @user.name # => "Steve Jobs"
    @user.version # => 2
    @user.versions.count # => 1
    @user.reset_to!(1)
    @user.name # => "Steve Richert"
    @user.version # => 1
    @user.versions.count # => 0

* Storing which user is responsible for a revision. Rather than introduce a lot of controller magic to guess what to store, you can simply update an additional attribute on your versioned model: <tt>updated_by</tt>.

    @user.update_attributes(:last_name => "Jobs", :updated_by => "Tyler")
    @user.versions.last.user # => "Tyler"

  Instead of passing a simple string to the <tt>updated_by</tt> setter, you can pass a model instance, such as an ActiveRecord user or administrator. The association will be saved polymorphically alongside the version.

    @user.update_attributes(:last_name => "Jobs", :updated_by => current_user)
    @user.versions.last.user # => #<User first_name: "Steven", last_name: "Tyler">

* Global configuration. The new <tt>vestal_versions</tt> Rails generator also writes an initializer with instructions on how to set application-wide options for the <tt>versioned</tt> method.

* Conditional version creation. The <tt>versioned</tt> method now accepts <tt>:if</tt> and <tt>:unless</tt> options. Each expects a symbol representing an instance method or a proc that will be evaluated to determine whether or not to create a new version after an update. An array containing any combination of symbols and procs can also be given.

    class User < ActiveRecord::Base
      versioned :if => :really_create_a_version?
    end

* Custom version classes. By passing a <tt>:class_name</tt> option to the <tt>versioned</tt> method, you can specify your own ActiveRecord version model. <tt>VestalVersions::Version</tt> is the default, but feel free to stray from that. I recommend that your custom model inherit from <tt>VestalVersions::Version</tt>, but that's up to you!

* A <tt>versioned?</tt> convenience class method. If your user model is versioned, <tt>User.versioned?</tt> will let you know.

* Soft Deletes & Restoration.  By setting <tt>:dependent</tt> to <tt>:tracking</tt> destroys will be tracked.  On destroy a new version will be created storing the complete details of the object with a tag of 'deleted'.  The object can later be restored using the <tt>restore!</tt> method on the VestalVersions::Version record.  The attributes of the restored object will be set using the attribute writer methods.  After a restore! is performed the version record with the 'deleted' tag is removed from the history.

    class User < ActiveRecord::Base
      versioned :dependent => :tracking
    end

    >> @user.version
    => 2
    >> @user.destroy
    => <User id: 2, first_name: "Steve", last_name: "Jobs", ... >
    >> User.find(2)
    => ActiveRecord::RecordNotFound: Couldn't find User with ID=2
    >> VestalVersions::Version.last
    => <VestalVersions::Version id: 4, versioned_id: 2, versioned_type: "User", user_id: nil, user_type: nil, user_name: nil, modifications: {"created_at"=>Sun Aug 01 18:39:57 UTC 2010, "updated_at"=>Sun Aug 01 18:42:28 UTC 2010, "id"=>2, "last_name"=>"Jobs", "first_name"=>"Stephen"}, number: 3, tag: "deleted", created_at: "2010-08-01 18:42:43", updated_at: "2010-08-01 18:42:43">
    >> VestalVersions::Version.last.restore!
    => <User id: 2, first_name => "Steven", last_name: "Jobs", ... >
    >> @user = User.find(2)
    => <User id: 2, first_name => "Steven", last_name: "Jobs", ... >
    >> @user.version
    => 2

== Thanks!

Thank you to all those who post {issues and suggestions}[http://github.com/laserlemon/vestal_versions/issues]. And special thanks to:

* splattael[http://github.com/splattael], who first bugged (and helped) me to write some tests for this thing
* snaury[http://github.com/snaury], who helped out early on with the <tt>between</tt> association method, the <tt>:dependent</tt> option and a conflict from using a method called <tt>changes</tt>
* sthapit[http://github.com/sthapit], who was responsible for the <tt>:only</tt> and <tt>:except</tt> options as well as showing me that I'm a dummy for storing a useless first version

To contribute to <tt>vestal_versions</tt>, please fork, hack away in the integration[http://github.com/laserlemon/vestal_versions/tree/integration] branch and send me a pull request. Remember your tests!