Allows for multiple “drafts” of a model which can be useful when developing:
Draft/Live Version of Pages, for examples
A workflow system whereby a live copy may need to be active while a draft copy is awaiting approval.
This was built to be able to be tacked on to existing models, so the data schema doesn't need to change at all for the model this is applied to. Drafts are actually stored in a nearly-identical table and there is a has_one relationship to this. This separation allows the base model to really be treated just as before without having to apply conditions in queries to make sure you are really getting the “live” (non-draft) copy: Page.all will still only return the non-draft pages. This separate table is backed by a model created on the fly as a constant on the original model class. For example if a Page has_draft, a Page::Draft class will exist as the model for the page_drafts table.
This gem requires ActiveRecord 3.0.
In your Gemfile:
## First Migration (If Creating base model and drafts at the same time): class InitialSchema < ActiveRecord::Migration [:articles, :article_drafts].each do |table_name| create_table table_name, :force => true do |t| t.references :article if table_name == :article_drafts t.string :title t.text :summary t.text :body t.date :post_date end end end ## Model Class class Article < ActiveRecord::Base has_draft end ## Exposed Class Methods & Scopes: Article.draft_class => Article::Draft Article.with_draft.all => (Articles that have an associated draft) Article.without_draft.all => (Articles with no associated draft) ## Usage Examples: article = Article.create( :title => "My Title", :summary => "Information here.", :body => "Full body", :post_date => Date.today ) article.has_draft? => false article.instantiate_draft! article.has_draft? => true article.draft => Article::Draft Instance article.draft.update_attributes( :title => "New Title" ) article.replace_with_draft! article.title => "New Title" article.destroy_draft! article.has_draft? => false
## First Migration (If Creating base model and drafts at the same time): class InitialSchema < ActiveRecord::Migration [:articles, :article_copies].each do |table_name| create_table table_name, :force => true do |t| t.integer :news_article_id if table_name == :article_copies t.string :title t.text :summary t.text :body t.date :post_date end end end ## Model Class class Article < ActiveRecord::Base has_draft :class_name => 'Copy', :foreign_key => :news_article_id, :table_name => 'article_copies' end ## Single Table Inheritance Example class InitialSchema < ActiveRecord::Migration [:elements, :element_drafts].each do |table_name| create_table table_name, :force => true do |t| t.integer :element_id if table_name == :element_drafts t.string :title t.text :content t.string :type end end end class Element < ActiveRecord::Base class Draft < ActiveRecord::Base def element_icon_path 'assets/images/default.png' end end module HasDraftCallbacks def before_instantiate_draft # Need to append ::Draft so that it knows to use the Draft class self.draft.type = self.type + '::Draft' end def before_replace_with_draft # We are storing drafts with the ::Draft on the end so we have to strip it self.type = self.draft.type.split(':') end end end class BlueElement < Element has_draft :belongs_to => :element, :extends => Element::Draft do def element_icon_path 'assets/images/blue.png' end end include Element::HasDraftCallbacks end class UnknownElement < Element has_draft :belongs_to => :element, :extends => Element::Draft include Element::HasDraftCallbacks end This allows us to call element_draft.element on any subclass of Element::Draft instead of needing to know to call element_draft.blue_element or element_draft.unknown_element. Note: calling has_draft will have no effect if the parent class has already executed has_draft.
There are three callbacks you can specify directly as methods:
class Article < ActiveRecord::Base has_draft def before_instantiate_draft # Do Something end def before_replace_with_draft # Do Something end def before_destroy_draft # Do Something end end
Extending the Draft Class
Because you don't directly define the draft class, you can specify a block of code to be run in its context by passing a block to has_draft:
class Article < ActiveRecord::Base belongs_to :user has_draft do belongs_to :last_updated_user def approve! self.approved_at = Time.now self.save end end end
This gem uses appraisal to test with different versions of the dependencies. See Appraisal first for which versions are tested.
# Just the gems locked in Gemfile.lock $ bundle exec rake test # All of the Appraisals: $ bundle exec rake all