Users, Contacts, and Friendships

contact.rb

class Contact < ActiveRecord::Base
  has_many :users
  has_many :friendships
end

friendship.rb

# This links up a user's contacts
class Friendship < ActiveRecord::Base
  belongs_to :user
  belongs_to :contact
end

user.rb

class User < ActiveRecord::Base
  belongs_to :contact                      # The user's own contact details
  has_many :friendships                    # Joins up user's friends
  has_many :friends, through: :friendships # Queries for user's friends
end

users_controller.rb

class UsersController < ApplicationController
  def show
    # This grabs both the user's contact details (:contact) and friends (:friends)
    @user = User.includes(:contact, :friends).find(params[:key])
  end
end