app/models/event.rb
class Event < ActiveRecord::Base
# Extends & Includes
# Associations (belongs_to, has_one, has_many, has_and_belongs_to_many, accepts_nested_attributes_for)
has_and_belongs_to_many :participants, class_name: 'User', join_table: :events_users, uniq: true
# Delegates
# Validations
# Scopes
# Callbacks (before_create, before_save...)
# Custom (as_activity, attache, bitmask, enum, friendly_id, monetize, pagination, ...)
# Methods
end