gistfile1.rb

# I'm looking for a tidy named scope or class method I can define for a User
# that will give me all the Events for which the user hasn't yet registered.

class Event < ActiveRecord::Base
  has_many :registrations
  has_many :users, through: :registrations, as: :registrants
end

class Registration < ActiveRecord::Base
  belongs_to :event
  belongs_to :user
end

class User < ActiveRecord::Base
  has_many :registrations
  has_many :events, through: :registrations
end