AssociatedScope

###Preloadable and reusable ActiveRecord scope

Associated scope allow to define ActiveRecord associations outside models as extention to an existing model associations.

class Post < ApplicationRecord
  has_many :comments
end

module TopComments
  include AssociatedScope
  
  associated_scope :top_comments, -> { rated.order('score DESC') }, source: :comments
end

class HomeController < ApplicationController
  def index
    @posts = Post.recent.preload(:top_comments).extending(TopComments)
  end
end

# home.html.erb
<% @posts.each do |post| %>
  <% post.top_comments.each {...} %>
<% end %>

WHY

Solving N+1 queries for custom scopes might be a complicated task. Same time ActiveRecord has a built in preloader.

WHAT

AssociatedScope allow to define preloadable association with a scope.

Installation

Add this line to your application's Gemfile:

gem 'associated_scope'

And then execute:

$ bundle

Or install it yourself as:

$ gem install associated_scope

Usage

define a module as:

class TopComments
  include AssociatedScope
  
  associated_scope :top_comments, -> { rated.order('score DESC') }, source: :comments
end

associated_scope <new association name>, <scope as lambda>, source: <base association>

extend relation with .extending(<module>)

Helper methods

Methods can be added to the target model as:

class TopComments
  include AssociatedScope
  
  associated_scope :top_comments, -> { rated.order('score DESC') }, source: :comments
  
  associated_methods do
    def full_name
      "#{comment_author.first_name} #{comment_author.last_name}"
    end
  end
end

full_name = Post.recent.preload(:top_comments).extending(TopComments).first.full_name

Model instance can be extendend as well:

post = Post.last
post.extend(TopComments)
full_name = post.full_name

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/2rba/associated_scope

License

The gem is available as open source under the terms of the MIT License.