HasHistory

This gem adds a simple but effective changes history to your ActiveRecord models. It is compatible with Rails but can be used without as well.

Installation

Add this line to your application's Gemfile:

gem 'has_history'

And then execute:

$ bundle

Or install it yourself as:

$ gem install has_history

First you have to set up has_history:

$ rails g has_history:install

and then migrate your database (rake db:migrate).

From then on whenever you add has_history to your ActiveRecord model like this:

class MyModel < ActiveRecord::Base
  ...
  has_history
  ...
end

An then you 'magically' have history for the changes. You can access history via

MyModel.history_entries

Each entry has a modifications attribute that contains the changes in array of hashes:

[{ attribute1 => {:before => value1_before, :after => value1_after} }, ..., { attributeN => {:before => valueN_before, :after => valueN_after} }]

has_history has a few options to control its behavior.

ignore_attributes controls which attributes are not included in the history tracking
updater_id sets to user who made the changes (it can be taken from the record or via some other method)
resolution_map holds foreign key references to attributes whose value is to be materializes (that is instead of post_id it is possible to save the title of the referenced post)

For more details see config/initializers/has_history.rb.

Configuration has defaults, can be set through the initializer, or can be passed in on a per-model base (as params to the has_model method).