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Rails plugin that provides the ability to soft delete models
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Copyright (C) 2008 Substantial and Andy Hartford <hartforda @ gmail.com> == acts_as_soft_deletable This plugin provides the ability to soft delete ActiveRecord models. When models are destroyed, they will be archived into a special deleted table. They can later be restored easily. class Artist < ActiveRecord::Base acts_as_soft_deletable # This will wrap the destroy method to provide soft delete # support and create a new ActiveRecord class called Artist::Deleted end model = Artist.find(34) model.destroy # removes row from artists table, and adds a row to # deleted_artists table # The deleted record can be retrieved several ways deleted = Artist::Deleted.find(34) # using the deleted class deleted = Artist.find_with_deleted(34) # using the live class deleted = Artist.find_with_deleted_by_id(34) # dynamic finds work too deleted.undestroy! # adds the row back to the artists table, and removes # if from the deleted_artists table restored = Artist.find(34) # The artist is restored with all the same # information. The updated_at column will be # Time.now if it exists. == Use with Rails 2.3+ Before using this with a new Rails 2.3 app, you may want to consider using the new default_scope feature (or named_scopes) with a deleted_at flag. See http://ryandaigle.com/articles/2008/11/18/what-s-new-in-edge-rails-default-scoping for a discussion about this. == Compare to acts_as_paranoid Acts_as_paranoid takes the approach of using a deleted_at flag in the models table. If the deleted_at column has a value, the row is considered 'deleted'. The problem with this approach is that all finds on the model have to exclude 'deleted' rows. This turns out be be a challenge. Acts_as_paranoid patches the ActiveRecord internals to accomplish this, but it is fragile and could break with future changes to ActiveRecord. Also, some of the more exotic finds currently don't work (has_many :through with polymorphism as of March 2008) and supporting them means running on an upgrade treadmill to keep up with the evolution of ActiveRecord. This plugin avoids these problems by allowing the row to be deleted and archiving it into another table. The behavior of ActiveRecord::Base#Find doesn't have to change which should mean that this plugin is more immune to breaking due to ActiveRecord development. Queries on the live table will also be faster in the case of lots of deleted rows, because they will be in a separate table. The biggest tradeoff is that deleted rows aren't visible through active record associations because they're in a different table. The only solution I could think of was to write proxies for the associations. But it would involve so much code that I figured it wasn't worth it. Another tradeoff is that the deleted table needs to be maintained along with the live table. For example, if the artists table adds a column in a future migration, then the deleted_artists table needs that column as well. A migration helper is available (see below) that will help keep the deleted table in sync. Also, a unit test helper is provided (again, see below) which adds unit tests to the model ensuring soft delete is working. If this is used, the test will fail if the deleted table gets out of sync. == Setup === Model Any ActiveRecord class that wants the soft delete functionality should add the following line to their class definition: class SomeModel < ActiveRecord::Base acts_as_soft_deletable ... === Migration and setup the deleted table with the following migration: class AddActsAsSoftDeletable < ActiveRecord::Migration def self.up SomeModel::Deleted.create_table end def self.down SomeModel::Deleted.drop_table end end Any changes to the original table (such as adding a column) should be reflected in the deleted table. Use the update_columns method: class AddSkuColumn < ActiveRecord::Migration def self.up add_column 'items', 'sku', :string Item::Deleted.update_columns # will add sku column end def self.down remove_column 'items', 'sku' Item::Deleted.update_columns # will remove sku column end end Note that update_columns will happily delete columns if asked. In this case a warning will be issued when the migration is run alerting the developer to the situation. This warning can be disabled, see: ActiveRecord::Acts::SoftDeletable#remove_column_warning_enabled= === Unit tests A model's soft delete capabilities can be easily unit tested by using this provided assert: def test_soft_delete_works # will run the model through a destroy and undestroy while making sure all values were saved assert_model_soft_deletes( items(:radar_detector) ) end Note : You may need to put the following in your test_helper.rb file if you see an error like 'NoMethodError: undefined method 'assert_model_soft_deletes'' when running your unit tests: require 'test/unit' include Test::Unit::ActsAsDeleted This was developed with Test::Unit in mind. Not sure how well it works with rspec. === Thanks * Substantial, my employer for letting me release this * acts_as_paranoid and technoweenie, for a plugin I've got good years of use out of * acts_as_versioned, who's approach influenced this plugin * Danimal, for the feedback on rubyonrails-talk