Ruby:::前缀有什么作用? [英] Ruby: what does :: prefix do?

问题描述

我正在阅读 Artifice 的来源，并看到:

I was reading through the source of Artifice and saw:

module Artifice
  NET_HTTP = ::Net::HTTP
  # ...
end

行: https://github.com/wycats/artifice/blob/master/lib/artifice.rb#L6

为什么不只是用Net::HTTP代替::Net::HTTP，即当您使用::作为前缀时是什么意思?

Why not just do Net::HTTP instead of ::Net::HTTP, i.e., what does it mean when you use :: as a prefix?

推荐答案

::是范围解析运算符.它的作用是确定可以在哪个作用域下找到模块.例如:

The :: is the scope resolution operator. What it does is determines what scope a module can be found under. For example:

module Music
  module Record
    # perhaps a copy of Abbey Road by The Beatles?
  end

  module EightTrack
    # like Gloria Gaynor, they will survive!
  end
end

module Record
  # for adding an item to the database
end

要从Music外部访问Music::Record，请使用Music::Record.

To access Music::Record from outside of Music you would use Music::Record.

要引用Music::EightTrack中的Music::Record，您可以简单地使用Record，因为它是在同一范围(Music的)中定义的.

To reference Music::Record from Music::EightTrack you could simply use Record because it's defined in the same scope (that of Music).

但是，要从Music::EightTrack访问负责与数据库接口的Record模块，您不能仅使用Record，因为Ruby认为您想要Music::Record.那时，您将使用范围解析运算符作为前缀，并指定全局/主范围:::Record.

However, to access the Record module responsible for interfacing with your database from Music::EightTrack you can't just use Record because Ruby thinks you want Music::Record. That's when you would use the scope resolution operator as a prefix, specifying the global/main scope: ::Record.

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