Ruby中类名前的双冒号? [英] Double colons before class names in Ruby?

问题描述

我在 Rails 中看到很多在类名之前使用双冒号.

I have seen a lot usage of double colons in Rails before class names.

例如:

require ::File.expand_path('../config/environment',  __FILE__)

我知道 Module::Class::Constant 是什么意思，但是 ::Class 呢?

I know what Module::Class::Constant means, but ::Class ?

推荐答案

这意味着你引用了顶级命名空间中的常量File.在这样的情况下这是有道理的:

It means that you're referring to the constant File from the toplevel namespace. This makes sense in situations like this:

class MyClass #1
end

module MyNameSpace
  class MyClass #2
  end

  def foo # Creates an instance of MyClass #1
    ::MyClass.new # If I left out the ::, it would refer to
                  # MyNameSpace::MyClass instead.
  end
end

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