Part 3

Upcase
8

Around the 45 minute mark, he introduces Concerns. The usage for these is a little different in rails 4, so here is the code you need to make sure the Following concern is included in your User model:

app/models/concerns/following.rb

module Following
  extend ActiveSupport::Concern

  included do
  ...
  end
end

app/models/user.rb

class User < ActiveRecord::Base
  include Following
  ...
end