ruby - 使用类作为哈希的键？

Question

我刚刚意识到我正在使用类类型作为哈希变量的键：（不完全是）

def add_to_cache(obj)
  @cache[obj.class] = [] unless @cache.has_key? obj.class
  @cache[obj.class] << obj
end

所以我很好奇是否有人可以解释它。有什么缺点吗？它是如何存储在内存中的？我应该将它（obj.class）转换为 Symbol 还是 String？

Answer 1

In ruby you can have any object being a key of a hash. The method hash of the object is called for the actual hashing. I assume this method is optimized enough and good enough for Class. Converting the class to string or symbol here is not needed.

Answer 2

I am guessing that your objective might be to keep track of all instances of a certain class. If that is the case, then you do not need to, and should not, cache them manually. To get all instances of class klass, do this:

ObjectSpace.each_object(klass).to_a