Ruby:C类包含模块M; 包括M中的模块N不影响C.什么给出？

Question

更详细地说,我有一个模块Narf,它为一系列类提供基本功能.具体来说,我想影响所有继承的类Enumerable.所以我include Narf在Enumerable.

Array是一个Enumerable默认包含的类.然而,它并没有受到Narf模块中后期包含的影响.

有趣的是,包含后定义的类Narf来自Enumerable.

例:

# This module provides essential features
module Narf
  def narf?
    puts "(from #{self.class}) ZORT!"
  end
end

# I want all Enumerables to be able to Narf
module Enumerable
  include Narf
end

# Fjord is an Enumerable defined *after* including Narf in Enumerable
class Fjord
  include Enumerable
end

p Enumerable.ancestors    # Notice that Narf *is* there
p Fjord.ancestors         # Notice that Narf *is* here too
p Array.ancestors         # But, grr, not here
# => [Enumerable, Narf]
# => [Fjord, Enumerable, Narf, Object, Kernel]
# => [Array, Enumerable, Object, Kernel]

Fjord.new.narf?   # And this will print fine
Array.new.narf?   # And this one will raise
# => (from Fjord) ZORT!
# => NoMethodError: undefined method `narf?' for []:Array

Answer 1

在写下我的问题时，我不可避免地找到了答案。这就是我的想法。如果我错过了一个明显的、更简单的解决方案，请告诉我。

问题似乎是模块包含压平了所包含模块的祖先，并包含了该. 因此，方法查找不是完全动态的，所包含模块的祖先链永远不会被检查。

实际上，ArrayknowEnumerable是祖先，但它不关心当前包含的内容Enumerable。

好处是您可以include再次模块，它会重新计算模块祖先链，并包含整个内容。因此，在定义并包含之后Narf，您可以重新打开Array并Enumerable再次包含，它也会得到Narf。

class Array
  include Enumerable
end
p Array.ancestors
# => [Array, Enumerable, Narf, Object, Kernel]

现在让我们概括一下：

# Narf here again just to make this example self-contained
module Narf
  def narf?
    puts "(from #{self.class}) ZORT!"
  end
end

# THIS IS THE IMPORTANT BIT
# Imbue provices the magic we need
class Module
  def imbue m
    include m
    # now that self includes m, find classes that previously
    # included self and include it again, so as to cause them
    # to also include m
    ObjectSpace.each_object(Class) do |k|
      k.send :include, self if k.include? self
    end
  end
end

# imbue will force Narf down on every existing Enumerable
module Enumerable
  imbue Narf
end

# Behold!
p Array.ancestors
Array.new.narf?
# => [Array, Enumerable, Narf, Object, Kernel]
# => (from Array) ZORT!

现在在GitHub和Gemcutter上享受更多乐趣。