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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 supports ActiveRecord 3, 4, and 5.

In your Gemfile:

gem "has_draft"

## 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(':')[0]
    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

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