# PaperTrail PaperTrail lets you track changes to your models' data. It's good for auditing or versioning. You can see how a model looked at any stage in its lifecycle, revert it to any version, and even undelete it after it's been destroyed. ## Features * Stores every create, update and destroy. * Does not store updates which don't change anything. * Does not store updates which only change attributes you are ignoring. * Allows you to get at every version, including the original, even once destroyed. * Allows you to get at every version even if the schema has since changed. * Allows you to get at the version as of a particular time. * Automatically records who was responsible if your controller has a `current_user` method. * Allows you to set who is responsible at model-level (useful for migrations). * Allows you to store arbitrary metadata with each version (useful for filtering versions). * Can be turned off/on (useful for migrations). * No configuration necessary. * Stores everything in a single database table (generates migration for you). * Thoroughly tested. * Threadsafe. ## Rails Version Known to work on Rails 2.3. Probably works on Rails 2.2 and 2.1. ## Basic Usage PaperTrail is simple to use. Just add 15 characters to a model to get a paper trail of every `create`, `update`, and `destroy`. class Widget < ActiveRecord::Base has_paper_trail end This gives you a `versions` method which returns the paper trail of changes to your model. >> widget = Widget.find 42 >> widget.versions # [, , ...] Once you have a version, you can find out what happened: >> v = widget.versions.last >> v.event # 'update' (or 'create' or 'destroy') >> v.whodunnit # '153' (if the update was via a controller and # the controller has a current_user method, # here returning the id of the current user) >> v.created_at # when the update occurred >> widget = v.reify # the widget as it was before the update; # would be nil for a create event PaperTrail stores the pre-change version of the model, unlike some other auditing/versioning plugins, so you can retrieve the original version. This is useful when you start keeping a paper trail for models that already have records in the database. >> widget = Widget.find 153 >> widget.name # 'Doobly' # Add has_paper_trail to Widget model. >> widget.versions # [] >> widget.update_attributes :name => 'Wotsit' >> widget.versions.first.reify.name # 'Doobly' >> widget.versions.first.event # 'update' This also means that PaperTrail does not waste space storing a version of the object as it currently stands. The `versions` method gives you previous versions; to get the current one just call a finder on your `Widget` model as usual. Here's a helpful table showing what PaperTrail stores:
Event Model Before Model After
create nil widget
update widget widget'
destroy widget nil
PaperTrail stores the values in the Model Before column. Most other auditing/versioning plugins store the After column. ## Ignoring changes to certain attributes You can ignore changes to certain attributes like this: class Article < ActiveRecord::Base has_paper_trail :ignore => [:title, :rating] end This means that changes to just the `title` or `rating` will not store another version of the article. It does not mean that the `title` and `rating` attributes will be ignored if some other change causes a new `Version` to be crated. For example: >> a = Article.create >> a.versions.length # 1 >> a.update_attributes :title => 'My Title', :rating => 3 >> a.versions.length # 1 >> a.update_attributes :content => 'Hello' >> a.versions.length # 2 >> a.versions.last.reify.title # 'My Title' ## Reverting And Undeleting A Model PaperTrail makes reverting to a previous version easy: >> widget = Widget.find 42 >> widget.update_attributes :name => 'Blah blah' # Time passes.... >> widget = widget.versions.last.reify # the widget as it was before the update >> widget.save # reverted Alternatively you can find the version at a given time: >> widget = widget.version_at(1.day.ago) # the widget as it was one day ago >> widget.save # reverted Note `version_at` gives you the object, not a version, so you don't need to call `reify`. Undeleting is just as simple: >> widget = Widget.find 42 >> widget.destroy # Time passes.... >> widget = Version.find(153).reify # the widget as it was before it was destroyed >> widget.save # the widget lives! In fact you could use PaperTrail to implement an undo system, though I haven't had the opportunity yet to do it myself. ## Finding Out Who Was Responsible For A Change If your `ApplicationController` has a `current_user` method, PaperTrail will store the value it returns in the `version`'s `whodunnit` column. Note that this column is a string so you will have to convert it to an integer if it's an id and you want to look up the user later on: >> last_change = Widget.versions.last >> user_who_made_the_change = User.find last_change.whodunnit.to_i In a migration or in `script/console` you can set who is responsible like this: >> PaperTrail.whodunnit = 'Andy Stewart' >> widget.update_attributes :name => 'Wibble' >> widget.versions.last.whodunnit # Andy Stewart ## Storing metadata You can store arbitrary metadata alongside each version like this: class Article < ActiveRecord::Base belongs_to :author has_paper_trail :meta => { :author_id => Proc.new { |article| article.author_id }, :answer => 42 } end PaperTrail will call your proc with the current article and store the result in the `author_id` column of the `versions` table. (Remember to add your metadata columns to the table.) Why would you do this? In this example, `author_id` is an attribute of `Article` and PaperTrail will store it anyway in serialized (YAML) form in the `object` column of the `version` record. But let's say you wanted to pull out all versions for a particular author; without the metadata you would have to deserialize (reify) each `version` object to see if belonged to the author in question. Clearly this is inefficient. Using the metadata you can find just those versions you want: Version.all(:conditions => ['author_id = ?', author_id]) ## Turning PaperTrail Off/On Sometimes you don't want to store changes. Perhaps you are only interested in changes made by your users and don't need to store changes you make yourself in, say, a migration. If you are about change some widgets and you don't want a paper trail of your changes, you can turn PaperTrail off like this: >> Widget.paper_trail_off And on again like this: >> Widget.paper_trail_on ## Installation 1. Install PaperTrail either as a gem (from Gemcutter; the ones on GitHub are obsolete) or as a plugin: `config.gem 'paper_trail', :source => 'http://gemcutter.org'` or: `script/plugin install git://github.com/airblade/paper_trail.git` 2. Generate a migration which will add a `versions` table to your database. `script/generate paper_trail` 3. Run the migration. `rake db:migrate` 4. Add `has_paper_trail` to the models you want to track. ## Testing PaperTrail has a thorough suite of tests. ## Articles [Keep a Paper Trail with PaperTrail](http://www.linux-mag.com/id/7528), Linux Magazine, 16th September 2009. ## Problems Please use GitHub's [issue tracker](http://github.com/airblade/paper_trail/issues). ## Contributors Many thanks to: * [Zachery Hostens](http://github.com/zacheryph) * [Jeremy Weiskotten](http://github.com/jeremyw) * [Phan Le](http://github.com/revo) * [jdrucza](http://github.com/jdrucza) ## Inspirations * [Simply Versioned](http://github.com/github/simply_versioned) * [Acts As Audited](http://github.com/collectiveidea/acts_as_audited) ## Intellectual Property Copyright (c) 2009 Andy Stewart (boss@airbladesoftware.com). Released under the MIT licence.