vendor/rails/activerecord/test/models/edge.rb

   1 # This class models an edge in a directed graph.
   2 class Edge < ActiveRecord::Base
   3   belongs_to :source, :class_name => 'Vertex', :foreign_key => 'source_id'
   4   belongs_to :sink,   :class_name => 'Vertex', :foreign_key => 'sink_id'
   5 end