63. あるクラスのサブクラスを取 得する class Object def subclasses_of(*superclasses) subclasses = [] superclasses.each do |sup| ObjectSpace.each_object(class << sup; self; end) do |k| if k != sup && (k.name.blank? || eval(quot;defined?(::#{k}) && ::#{k}.object_id == k.object_idquot;)) subclasses << k end end end subclasses end end 62/67