Rails5 following migration file

create_user_relationships.rb

class CreateUserRelationships < ActiveRecord::Migration[5.2]
  def change
    create_table :user_relationships do |t|
      t.references :follower, foreign_key: { to_table: :users }
      t.references :followed, foreign_key: { to_table: :users }

      t.timestamps

      t.index [:follower_id, :followed_id], unique: true
    end
  end
end

user.rb

class User < ApplicationRecord
  has_many :active_relationships, class_name:  :UserRelationship,
                                  foreign_key: :follower_id,
                                  dependent:   :destroy
  has_many :passive_relationships, class_name:  :UserRelationship,
                                  foreign_key: :followed_id,
                                  dependent:   :destroy
  has_many :following, through: :active_relationships, source: :followed
  has_many :followers, through: :passive_relationships, source: :follower
end

user_relationship.rb

class UserRelationship < ApplicationRecord
	belongs_to :followed, class_name: :User
	belongs_to :follower, class_name: :User
end