Build Robust & Production Quality Applications - Lesson 6: ActiveSupport::Concerns

In our Todos example, we created a method

before_create :generate_token

for and then defined the generate_ token method under private, within the Todos model.

But what if you want to include this in several models? DRY does not only mean "Dont Repeat Yourself", but it also means to have one authoritative source for method calls

That's where ActiveSupport::Concerns can help by basically extracting the common code into a module

lib/tokenable.rb
module Tokenable
extend ActiveSupport::Concern

  included do
    before_create :generate_token
  end

  def generate_token
    self.token = SecureRandom.urlsafe_base64
  end
end

Then in the Todo model:

class Todo < ActiveRecord::Base
  include Tokenable

With Rails 3 or later, the lib directory is no longer automatically loaded You instead have to:

require_relative '../..lib/tokenable'

class Todo < ActiveRecord::Base
  include Tokenable

end

Now if you dont want to require_relative everytime: You can do one of the two:

1. move the Tokenable file to your models folder
2. go to /enviornments/application.rb config.autoload_paths << "#{Rails.root}/lib"

then remove require_relative from the model.