Really that should be “Bi-directional self-referential relationships in ActiveRecord models”, but that’s just too much to say!

A common example for this would be if you had a Person model and a Friendship model, and you wish the friendship between two people to be a two-way road, like on Facebook. The project I’m working on is a genealogy application that has partnerships (eg. marriage) between two people, but it’s the same deal.

Now typically, :has_many relationships in ActiveRecord are uni-directional. You have to do a little bit of trickery to get it to happen both ways. Here’s the code.

[Read more →]