ruby - 优雅的方式添加到已经包含的模块？

Question

我想对一个 gem 进行猴子修补，目标代码在一个模块中。不幸的是，在我预先准备我的补丁时，该模块已经包含在各种类中，新代码无效。

例子:

module Feature
  def action
    puts "Feature"
  end
end

module Patch
  def action
    puts "Patch"
  end
end

class Base1
  include Feature
end

Feature.prepend Patch

class Base2
  include Feature
end


Base1.new.action # Returns "Feature", I want it to be "Patch" instead.
Base2.new.action # Returns "Patch"

当我在 Feature 被包含到 Base2 之前添加前缀时，补丁可以工作，但是对于真正的 gem 我不能改变顺序。

有没有一种优雅的方法可以解决这个问题，还是我必须遍历 ObjectSpace 才能找到哪些类已经包含了 Feature 模块？

Answer 1

TL;DR – 通常不能，但是 Base1.include Patch可能已经足够好了。

---

对于您的示例代码， ancestors 的 Base1和 Base2是:(为清楚起见对齐)

Base1.ancestors #=> [Base1,        Feature, Object, Kernel, BasicObject]
Base2.ancestors #=> [Base2, Patch, Feature, Object, Kernel, BasicObject]

Base2有一个额外的祖先Patch之前 Feature – Feature.prepend Patch 的结果.

Ruby 不允许我们随意修改模块的祖先链，所以我们不能只在前面加上 Patch至 Feature追溯。

但幸运的是，Patch是 Base 之后的第一个模块类，所以我们可以求助于 include 附加Patch至 Base1相反:

Base1.include Patch
Base1.ancestors #=> [Base1, Patch, Feature, Object, Kernel, BasicObject]

显然，这只适用于非常特殊的情况，而不适用于一般情况。

这是一个反例:

module Feature
  def action ; 'Feature' ; end
end

module Foo
  def action ; "#{super} overridden" ; end
end

module Patch
  def action ; 'Patch' ; end
end

class Base1
  include Feature
  include Foo
end

Feature.prepend(Patch)

class Base2
  include Feature
  include Foo
end

Base1.new.action #=> "Feature overridden"
Base2.new.action #=> "Patch overridden"

Base1.include Patch

Base1.new.action #=> "Patch"

看老祖宗揭示问题:

Base1.ancestors #=> [Base1, Foo,        Feature, Object, Kernel, BasicObject]
Base2.ancestors #=> [Base2, Foo, Patch, Feature, Object, Kernel, BasicObject]
Base1.include Patch
Base1.ancestors #=> [Base1, Patch, Foo, Feature, Object, Kernel, BasicObject]

Patch和 Foo有问题。