有人可以解释一下 class <<自我对我? [英] Can someone please explain class << self to me?

问题描述

我是第一次进入 Rails 编程，在查看我下载的一些库的代码时，我偶尔会注意到代码:

I'm jumping into rails programming for the first time and while looking at the code for some libraries I've downloaded, I occasionally notice the code:

class << self
  def func
     stuff
  end
end

我试过在网上搜索解释，但是 <<从大多数有用的搜索引擎中删除，因此它最终只搜索 class self，这不是很有用.任何见解将不胜感激.

I've tried searching the web for an explanation, but the << gets stripped from most useful search engines, so it ends up just searching for class self, which isn't very useful. Any insight would be appreciated.

推荐答案

在 Ruby 中，class <<foo 打开foo 引用的对象的单例类.在 Ruby 中，每个对象都有一个与之关联的单例类，它只有一个实例.这个单例类包含特定于对象的行为，即单例方法.

In Ruby, class << foo opens up the singleton class of the object referenced by foo. In Ruby, every object has a singleton class associated with it which only has a single instance. This singleton class holds object-specific behavior, i.e. singleton methods.

所以，class <<self 打开了 self 的单例类.self 是什么，当然取决于你所处的环境.例如，在模块或类定义体中，它是模块或类本身.

So, class << self opens up the singleton class of self. What exactly self is, depends on the context you are in, of course. In a module or class definition body, it is the module or class itself, for example.

如果您使用单例类的目的只是定义单例方法，那么实际上有一个快捷方式:def foo.bar.

If all you are using the singleton class for, is defining singleton methods, there is actually a shortcut for that: def foo.bar.

以下是如何使用单例方法提供一些与特定实例没有任何关联的过程"的示例:

Here's an example of how to use singleton methods to provide some "procedures" which don't really have any association with a particular instance:

class << (Util = Object.new)
  def do_something(n)
    # ...
  end
end

Util.do_something(n)

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