by Ole Friis Østergaard

= Why do versioning?

== Which problems do we solve?

- The user regrets pressing that "Delete project" button
- You want to track the changes to certain objects
- You need to know who changed an object




= Walk-through of Rails plug-ins

- Rails makes it easy to be creative when doing plug-ins
- Really simple pieces of code that do exiting stuff
- Very non-intrusive
- Easy to use


== acts_as_logged

- Makes a "shadow copy" of your normal database entries
- Makes it easy to comply with laws concerning logging
- Cannot show the history
- Created by some of my colleages at Trifork
- Not official homepage

=== How it works

Add :history => true to create_table and drop_table statements in your migrations
It will create a "shadow copy" of the table

In the model: acts_as_logged statement
Whenever a model object is saved, updated, or deleted, a new record is created in the table_name_history table


== acts_as_versioned

- Makes "shadow copies" of rows in the database
- Makes it possible to view these old versions

=== What to do

Annotate models with "acts_as_versioned"
Don't access associations in the views
Add a version column to the table to be versioned
Add a new table called org_table_versioned

Use the find_version method on models to access previous versions

=== Issues

Associations does not work as expected when showing a previous version
Adds an extra table to each of your tables

=== How does it work

Returns OriginalClass::Version class for previous versions


== acts_as_paranoid

Calling destroy simply sets a "deleted_at" flag
Therefore, deleted objects can still be found
Not really a versioning plugin, but has a purpose

Modifies finder and update methods to know about deleted methods
Just add the deleted_at column to the table

=== Issues

Not protected against updates, since it doesn't version
You have to do a little to make it work with acts_as_versioned


== acts_as_versioned_association

Extends acts_as_versioned to support associations


== Rails Undo Redo

Undo/redo user actions

=== How to use it

Controllers: Call "undoable_methods" in class definition
Models: Annotate with "acts_as_undoable"
Routes: 
- map.undo  'undo', :controller => 'projects', :action => :undo
- map.redo  'redo', :controller => 'projects', :action => :redo
Copy migration from plugin migration folder

In the view:
<%= undo_redo_links %>

In controller actions:
	change("Update project #{@project.name}", projects_path, projects_path) do
		... normal action code ...
	end


== acts_subversive

His own plugin:
- Can go back in time
- Can follow association 

== How it works

In your migrations:
- create_version_number_table (just once)
- create_versioned_table and drop_versioned_table for each table

In your models:
- acts_subversive

In your controllers:
- use the find_version finder

== Issues

- has_and_belongs_to_many unsupported
- Inheritance unsupported
- (n+1) ew tables when versioning n classes


=