`if __FILE__ == $0` 在 Ruby 中是什么意思 [英] What does `if __FILE__ == $0` mean in Ruby

问题描述

if __FILE__ == $0
  $:.unshift File.join(File.dirname(__FILE__),'..')

我在 Ruby 中找到了这段代码，是什么意思?

I found this code in Ruby, what's the meaning?

推荐答案

# Only run the following code when this file is the main file being run
# instead of having been required or loaded by another file
if __FILE__==$0
  # Find the parent directory of this file and add it to the front
  # of the list of locations to look in when using require
  $:.unshift File.expand_path("../../", __FILE__)  
end

请注意，随着 require_relative 的出现，通常不需要这种特殊做法(添加到 LOAD_PATH 目录)，并且 expand_path 是一种更简单的查找父目录的方法.

Note that this particular practice (adding to the LOAD_PATH directory) is not usually necessary with the advent of require_relative, and expand_path is a simpler way of finding the parent directory.

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