Ruby on rails - Reference the same model twice?

Question

Is it possible to set up a double relationship in activerecord models via the generate scaffold command?

For example, if I had a User

Answer 1

The above answers, while excellent, do not create foreign key constraints in the database, instead only creating indexes and bigint columns. To ensure that the foreign key constraint is enforced, add the following to your migration:

class CreatePrivateMessages < ActiveRecord::Migration[5.1]
    def change
        create_table :private_messages do |t|
          t.references :sender
          t.references :recipient
        end

        add_foreign_key :private_messages, :users, column: :sender_id, primary_key: :id
        add_foreign_key :private_messages, :users, column: :recipient_id, primary_key: :id
    end
end

This will ensure that the indices get created on the sender_id and recipient_id as well as the foreign key constraints in the database you're using.