Ruby: Module, Mixins and Blocks confusing?

Question

Following is the code I tried to run from the Ruby Programming Book http://www.ruby-doc.org/docs/ProgrammingRuby/html/tut_modules.html

Why doesn\'t the

Answer 1

By the way: in Ruby 2.0, there are two features which help you with both your problems.

Module#prepend prepends a mixin to the inheritance chain, so that methods defined in the mixin override methods defined in the module/class it is being mixed into.

Refinements allow lexically scoped monkeypatching.

Here they are in action (you can get a current build of YARV 2.0 via RVM or ruby-build easily):

module Sum
  def sum(initial=0)
    inject(initial, :+)
  end
end

module ArrayWithSum
  refine Array do
    prepend Sum
  end
end

class Foo
  using ArrayWithSum

  p [1, 2, 3].sum
  # 6
end

p [1, 2, 3].sum
# NoMethodError: undefined method `sum' for [1, 2, 3]:Array

using ArrayWithSum
p [1, 2, 3].sum
# 6