From: Shugo Maeda <shugo@...>
Date: 2010-11-25T13:35:39+09:00
Subject: [ruby-core:33352] Re: [Ruby 1.9-Feature#4085] Refinements and nested methods

Hi,

Thanks for you comment.

2010/11/25 Dave Thomas <redmine@ruby-lang.org>:
> �module Quux
> � �using FooExt
>
> � �foo = Foo.new
> � �foo.bar �# => FooExt#bar
> � �foo.baz �# => Foo#bar
> �end
>
> This behavior makes me nervous�I can see arguments for it, but at the same time I can see in leading to problems, particularly in well structured classes where a large set of behaviors is defined in terms of one method. I'm sure the syntax below is wrong, but look at the spirit of it.
>
> �module DoubleEach
> � �refine Array do
> � � �def each
> � � � � super do |val|
> � � � � � yield 2*val
> � � � � end
> � � �end
> � �end
> �end
>
> �using DoubleEach
>
> �[ 1, 2, 3 ].each {|v| p v } � #=> 2, 4, 6
>
> �[ 1, 2, 3 ].min � �#=> 1

The syntax right and currently [1,2,3].min returns 2.
However, It's a bug (methods implemented by C behave wrong),
and I think it should return 1 as you showed above.

> That would be surprising to me, as I'd expect the behavior of all the Enumerable methods, which depend on each, to change if I change the behavior of each.

However, some other person might expect the original behavior of each.
For example,

  class Foo
     using DoubleEach

     def bar
       SomeOtherModule.do_something # DoubleEach may break this method
     end
  end

If SomeOtherModule.do_something is implemented by someone else, and
Array#each is used in do_something, DoubleEach breaks the code.
If you'd like to change the behavior of callees, you can use monky
patching or singleton methods instead of refinements.

-- 
Shugo Maeda