ruby - 如何覆盖 Kernel.load

Question

我需要覆盖 Kernel.load为了观察和处理我们为监控而编写的一些 Ruby 文件。然而，它似乎不受此类恶作剧的影响。

很容易覆盖require和 require_relative ，但是 load 位于它们之下，如果我没记错的话，会成为读取实际文件的瓶颈。

这就是为什么它似乎不受覆盖的原因:

Kernel.module_eval do

  alias_method :original_require, :require
  def require(filename)
    require_result = original_require(filename)
    puts "required #{filename}"

    require_result
  end

  alias_method :original_load, :load
  def load(filename, wrap=true)
    load_result = original_load(filename, wrap)
    puts "loaded #{filename}"

    load_result
  end
end
include Kernel

require 'open-uri'
puts 'done'

运行输出:

required uri/rfc2396_parser
required uri/rfc3986_parser
required uri/common
required uri/common
required uri/generic
required uri/generic
required uri/ftp
required uri/generic
required uri/http
required uri/http
required uri/https
required uri/generic
required uri/ldap
required uri/ldap
required uri/ldaps
required uri/generic
required uri/mailto
required uri
required stringio
required date_core
required date
required time
required open-uri
done

我满足于只覆盖 require 和 require_relative。不过，我很好奇 load 发生了什么。

---

事后思考:

看起来 load 不是由 require 或 require_relative 调用的。我认罪。抓得好Matt .

这个问题类似于“How to override require in Ruby?”。

良好的阅读:

• "Ways to load code "
• "Ruby Require VS Load VS Include VS Extend "
• 和Jörg's “When monkey patching a method, can you call the overridden method from the new implementation?”中的惊人答案

Jörg's评论

I also want to give some love to Module#prepend, which would allow you to simply use super instead of that ugly alias_method stuff, with the additional bonus that your modifications would actually show up in the ancestry chain and thus much easier to debug.

非常明智，值得使用。

• http://ruby-doc.org/core-2.2.2/Module.html#method-i-prepend
• http://ruby-doc.org/core-2.2.2/Module.html#method-i-prepend_features
• http://ruby-doc.org/core-2.2.2/Module.html#method-i-append_features

Answer 1

这里有两个简单的示例，它们似乎可以覆盖 require 和 require_relative，基于“When monkey patching a method, can you call the overridden method from the new implementation?”中的示例。

module Kernel
  old_require = method(:require)
  define_method(:require) do |filename|
    puts "require #{filename}"
    old_require.call(filename)
  end

  old_require_relative = method(:require_relative)
  define_method(:require_relative) do |filename|
    puts "require_relative #{filename}"
    old_require_relative.call(filename)
  end
end

或

module KernelExtensions
  def require(filename)
    puts "require #{filename}"
    super
  end
  def require_relative(filename)
    puts "require_relative #{filename}"
    super
  end
end

class Object
  prepend KernelExtensions
end

运行第二个使用

module Kernel
  prepend KernelExtensions
end

没有用，但由于 Object 包含内核，使用 class Object 覆盖似乎工作得很干净。