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GroupedScope: Has Many Associations IN (GROUPS)

GroupedScope aims to make two things easier in your ActiveRecord models. First, provide an easy way to group objects. Second, to allow the group to share association collections via existing has_many relationships. See installation and usage for more details.

Installation & Usage

Install the gem with bundler.

gem 'grouped_scope'

To use GroupedScope on a model it must have a :group_id column.

class AddGroupId < ActiveRecord::Migration
  def up
    add_column :employees, :group_id, :integer
  def down
    remove_column :employees, :group_id

Assume the following model.

class Employee < ActiveRecord::Base
  has_many :reports
  grouped_scope :reports

By calling grouped_scope on any association you create a new group accessor for each instance. The object returned will act just like an array and at least include the current object that called it.   # => [#<Employee id: 1, group_id: nil>]

To group resources, just assign the same :group_id in the schema.

@employee_one.update_attribute :group_id, 1
@employee_two.update_attribute :group_id, 1   # => [#<Employee id: 1, group_id: 1>, #<Employee id: 2, group_id: 1>]

Calling grouped_scope on the :reports association leaves the existing association intact.

@employee_one.reports  # => [#<Report id: 2, employee_id: 1>]
@employee_two.reports  # => [#<Report id: 18, employee_id: 2>, #<Report id: 36, employee_id: 2>]

Now the good part, all associations passed to the grouped_scope method can be called on the group proxy. The collection will return resources shared by the group. # => [#<Report id: 2, employee_id: 1>, 
                                  #<Report id: 18, employee_id: 2>, 
                                  #<Report id: 36, employee_id: 2>]

You can even call scopes or association extensions defined on the objects in the collection defined on the original has_many. For instance:

Todo List

  • Add more GroupedScope::Grouping code.
  • Add polymorphic support.
  • Add :through support.
  • Raise errors and/or support :finder_sql/:counter_sql.
  • Add a user definable group_id schema.


Simple! Just clone the repo, then run bundle install and bundle exec rake. The tests will begin to run. We also use Travis CI to run our tests too. Current build status is:

Build Status


Released under the MIT license. Copyright (c) 2011 Ken Collins

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