Bidirectional self referential associations

Question

Taking Ryan Bates\' asciicast as an example: http://asciicasts.com/episodes/163-self-referential-association

He ends with two associations of User

• :fri

Answer 1

see if this works for you?

class User < ActiveRecord::Base
  has_many :friendships, :foreign_key => "person_id", :class_name => "Friendship"
  has_many :friends, :through => :friendships

  def befriend(user)
    # TODO: put in check that association does not exist
    self.friends << user
    user.friends << self
  end
end

class Friendship < ActiveRecord::Base
  belongs_to :person, :foreign_key => "person_id", :class_name => "User"
  belongs_to :friend, :foreign_key => "friend_id", :class_name => "User"  
end

# Usage
jack = User.find_by_first_name("Jack")
jill = User.find_by_first_name("Jill")

jack.befriend(jill)

jack.friends.each do |friend|
  puts friend.first_name
end
# => Jill

jill.friends.each do |friend|
  puts friend.first_name
end
# => Jack

this is given a database table schema of

users
  - id
  - first_name
  - etc...

friendships
  - id
  - person_id
  - friend_id