Avo::ApplicationController

On extending the ApplicationController

You may sometimes want to add functionality to Avo's ApplicationController. That functionality may be setting attributes to Current or multi-tenancy scenarios.

When you need to do that, you may feel the need to override it with your own version. That means you go into the source code, find AVO_REPO/app/controllers/avo/application_controller.rb, copy the whole thing into your own YOUR_APP/app/controllers/avo/application_controller.rb file inside your app, and add your own piece of functionality.

# Copied from Avo to `app/controllers/avo/application_controller.rb`
module Avo
  class ApplicationController < ::ActionController::Base
    include Pagy::Backend
    include Avo::ApplicationHelper
    include Avo::UrlHelpers

    protect_from_forgery with: :exception
    around_action :set_avo_locale
    before_action :multitenancy_detector

    # ... more Avo::ApplicationController methods

    def multitenancy_detector
      # your logic here
    end
  end
end

That will work just fine until the next time we update it. After that, we might add a method, remove one, change the before/after actions, update the helpers and do much more to it. That will definitely break your app the next time when you upgrade Avo. Avo's private controllers are still considered private APIs that may change at any point. These changes will not appear in the changelog or the upgrade guide.

Responsibly extending the ApplicationController

There is a right way of approaching this scenario using Ruby modules or concerns.

First, you create a concern with your business logic; then you include it in the parent Avo::ApplicationController like so:

# app/controllers/concerns/multitenancy.rb
module Multitenancy
  extend ActiveSupport::Concern

  included do
    before_action :multitenancy_detector
  end

  def multitenancy_detector
    # your logic here
  end
end

# configuration/initializers/avo.rb
Rails.configuration.to_prepare do
  Avo::ApplicationController.include Multitenancy
end

With this technique, the multitenancy_detector method and its before_action will be included safely in Avo::ApplicationController.