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

为什么不直接使用Net::HTTP 而不是::Net::HTTP，即使用::是什么意思code> 作为前缀?

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

:: 是作用域解析操作符.它的作用是确定可以在什么范围内找到模块.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，您可以使用 Music::Record.

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

要从 Music::EightTrack 引用 Music::Record 您可以简单地使用 Record 因为它定义在相同的范围内(即音乐).

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 访问负责与数据库交互的 Record 模块，您不能只使用 Record，因为Ruby 认为你想要 Music::Record.那时您将使用范围解析运算符作为前缀，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.

这篇关于Ruby: :: 前缀有什么作用?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！