boom.rb

class User < ActiveRecord::Base
	has_many :activities

  # Ativamente... os que eu sigo

  has_many :active_relationships, class_name:  'Relationship', foreign_key: 'follower_id', dependent: :destroy
  has_many :following, through: :active_relationships, source: :followed
  
end

class Activity < ActiveRecord::Base
	belongs_to :subject, polymorphic: true
	belongs_to :user
end

class Relationship < ActiveRecord::Base
	belongs_to :follower, class_name: 'User'
  belongs_to :followed, class_name: 'User'
end