# parent.rb class Parent < ActiveRecord::Base has_many :children def has_parent? ... end end # child.rb class Child < ActiveRecord::Base belongs_to :parent end > child = Child.find(1) > child.parent.has_parent? # 冗長な感じがする # child.rb をこう書くと require 'forwardable' class Child < ActiveRecord::Base extend Forwardable belongs_to :parent def_delegator :parent, :has_parent?, :has_grandparent? end # こう書ける!