How to model a mutual friendship in Rails

Question

I know this question has been asked before on Stack Overflow, but the answers aren\'t doing it for me in ways I can explain. My general approach was inspired by this tutoria

Answer 1

Maybe this:

friendship.rb
belongs_to :friend_one, :foreign_key => :user_id
belongs_to :friend_two, :foreign_key => :friendship_id

and

user.rb

has_many :friendship_ones, :class_name => 'Friendship', :foreign_key => :friendship_id
has_many :friend_ones, through: :friendship_ones
has_many :friendship_twos, :class_name => 'Friendship', :foreign_key => :user_id
has_many :friend_twos, through: :friendship_twos


def friends
  friend_ones + friend_twos
end

You get two queries to find the friends, but it is a simple data model and you you do just call @user.friends to find the instances.

It would be amenable to eager loading, if you load the two friend_ones and friend_twos associations.