From: Michael Schuerig <michael@...>
Date: 2005-09-12T00:41:32+09:00
Subject: Re: When an Array is not

David A. Black wrote:

> Hi --
> 
> On Sun, 11 Sep 2005, Michael Schuerig wrote:
> 
>>
>> (1) Under what circumstances is an array not an Array? I'm confronted
>> with such a case in one of my unit tests. The test failed when run in
>> conjunction with other tests and I narrowed it down to this: In the
>> tested code I use something.kind_of?(Array). I have a mixin module
>> that extends Array with additional methods. When this module is
>> required directly or indirectly in my test class then kind_of?(Array)
>> doesn't behave as expected anymore.
> 
> Can you provide a complete (non-)working example?  I can't quite
> reconstruct it from this.

Attached below with resolution. When copying and pasting the minimally
necessary pieces to recreate the failure I found the cause. The module
where the failure occurs has a sibling module named Array. Ruby
resolved the unadorned Array to this module, not the built-in class
Array.

Michael


require 'test/unit'

module BoilerPlate #:nodoc:
  module CoreExtensions #:nodoc:
    module Array #:nodoc:
    end
  end
end

module BoilerPlate # :nodoc:
  module CoreExtensions # :nodoc:
    module Hash # :nodoc:
      module Misc
        def value_to_a(key, default = [])
          if value = self[key]
            # ::Array is necessary to refer to the globally scoped Array
            # Array alone refers to the sibling module Array
            value.kind_of?(::Array) ? value : [ value ]
          else
            default
          end
        end
      end
    end
  end
end

Hash.class_eval do
  include BoilerPlate::CoreExtensions::Hash::Misc
end

class HashMiscTest < Test::Unit::TestCase
  def test_value_to_a_array
    options = { 'mykey' => [ 'thevalue', 'anothervalue' ] }
    assert_equal(['thevalue', 'anothervalue'],
      options.value_to_a('mykey'))
  end
end

-- 
Michael Schuerig                         Those people who smile a lot
mailto:michael@schuerig.de                             Watch the eyes
http://www.schuerig.de/michael/    --Ani DiFranco, Outta Me, Onto You