“Module＃singleton_class”的反向 [英] Inverse of `Module#singleton_class`

问题描述

Module＃singleton_class 的逆是什么？对我有用[0]丢个板砖[0]引用回复举报|收藏| 3楼|打赏|回复|评论楼主： =http://ruby-doc.org/core-2.2.0/ObjectSpace.html#method-c-each_object =nofollow> ObjectSpace＃each_object ：

 模块M; end 
 sc = M.singleton_class 
 
 ObjectSpace.each_object（Module）.find {| m | m.singleton_class == sc} 
＃=> M 
  

编辑：@ndn指出：

  ObjectSpace.each_object（sc）.to_a＃=> [M] 
  

因此只是：

  ObjectSpace.each_object（sc）.first＃=> M 
  

What is the inverse of Module#singleton_class? I.e., given a singleton class, how can I get the module it is the singleton of?

解决方案

You can use ObjectSpace#each_object for that:

module M; end
sc = M.singleton_class

ObjectSpace.each_object(Module).find { |m| m.singleton_class == sc }
  #=> M

Edit: @ndn has pointed out that:

ObjectSpace.each_object(sc).to_a #=> [M]

so it's just:

ObjectSpace.each_object(sc).first #=> M

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