Sharing common code between Rails controllers with `Scoped` pattern

If you follow a strict REST / nested resources approach to building your Rails app, you might get sick of repeating common controller actions.

Try the Scoped concern pattern: a place to put shared code (setting variables, authorization) and slim down your controllers.

Usage

This particular pattern comes from DHH and Basecamp a codebase that prides itself of using lots of tiny concerns to share bits of behavior.

While the savings of repeating the same before_actions to look up a Channel would be a fine benefit on its own, the naming convention of Scoped is such a great, sharp name. Playlists are scoped to a channel so it makes total sense that the corresponding controller would be channel scoped.

module ChannelScoped  extend ActiveSupport::Concern  included do    before_action :set_channel, :authorize_channel  end  private  def set_channel    @channel = Channel.find(params[:channel_id])  end  def authorize_channel    authorize @channel # check that user has access, etc  endendclass Channels::SubscriptionsController < ApplicationController  include ChannelScopedendclass Channels::VideosController < ApplicationController  include ChannelScopedendclass Channels::PlaylistsController < ApplicationController  include ChannelScopedend

Additional Resources

DHH Gist: Models for Nested Resources