I ran into a problem a while back of creating draft copies of ActiveRecord models for the purpose of establishing a draft/live system. I've since found a reason to resurrect this and publish it to GitHub and clean some things up. Check out has_draft on GitHub.
has_draft 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.
The semantics of this as well as most of the inspiration comes from version_fu, an excellent plugin for a similar purpose of maintaining several "versions" of a model.
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. As such, 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.
## 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
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
Block of Code Run for 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