In the example with monsters, perhaps the issue is that all the different monster types are classes instead of data. For instance, I would instead implement so

In the example with monsters, perhaps the issue is that all the different monster types are classes instead of data. For instance, I would instead implement something like class Monster attr_reader :type def initialize(type, likes = {}) @type = type @likes = likes end def likes?(x) @likes[x.type] end end orc = Monster.new(:orc) troll = Monster.new(:troll) elf = Monster.new(:elf) elf_maiden = Monster.new(:elf_maiden, :elf => true) puts troll.likes?(elf) puts elf_maiden.likes?(elf) If you have 150 subclasses, it is a code smell in the first place, and perhaps by addressing the root problem, issues like the one Steve mentions won't occur in the first place.