###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 %>Solving N+1 queries for custom scopes might be a complicated task. Same time ActiveRecord has a built in preloader.
AssociatedScope allow to define preloadable association with a scope.
Add this line to your application's Gemfile:
gem 'associated_scope'And then execute:
$ bundle
Or install it yourself as:
$ gem install associated_scope
define a module as:
class TopComments
include AssociatedScope
associated_scope :top_comments, -> { rated.order('score DESC') }, source: :comments
endassociated_scope <new association name>, <scope as lambda>, source: <base association>
extend relation with .extending(<module>)
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_nameModel instance can be extendend as well:
post = Post.last
post.extend(TopComments)
full_name = post.full_nameBug reports and pull requests are welcome on GitHub at https://github.com/2rba/associated_scope
The gem is available as open source under the terms of the MIT License.