From: Robert Klemme <shortcutter@...>
Date: 2010-12-01T18:22:55+09:00
Subject: Re: Object#each ?

On Wed, Dec 1, 2010 at 12:00 AM, Andrew Wagner <wagner.andrew@gmail.com> wrote:
> On Tue, Nov 30, 2010 at 4:40 PM, Robert Klemme
> <shortcutter@googlemail.com>wrote:
>
>> On 11/30/2010 06:45 PM, Andrew Wagner wrote:
>>
>>> On Tue, Nov 30, 2010 at 12:44 PM, Andrew Wagner<wagner.andrew@gmail.com
>>> >wrote:
>>>
>>>  A weird idea just popped into my head:
>>>>
>>>> class Object
>>>>   def each
>>>>     yield self
>>>>   end
>>>> end
>>>>
>>>> Lets you enumerate without having to worry about whether or not you have
>>>> a
>>>> collection. Thoughts? Hidden ramifications?
>>>
>> First of all if you implement #each then you should also include Enumerable
>> because the expectation would be that you also have all the nice methods
>> like #select, #map etc.  This makes all objects Enumerable which does not
>> seem a good idea.
>
> An interesting point. I think I agree that cluttering Object with all the
> Enumerable methods seems like a bad idea. I guess my thinking was that this
> would be useful just for the purposes of having #each available, without
> including Enumerable. This avoids the [*items] garbage.

I usually opt for making things explicit - at least if they are so
clutterless as "[*items]". :-)

>> One drawback of this approach is that you won't notice if you accidentally
>> pass something to a method which should be Enumerable (I mean a real
>> collection) - or at least the issue might take some time to be detected.
>
>  This is an interesting argument, because it sounds an awful lot like the
> arguments I usually hear against duck-typing and dynamic typing in general.
> Don't those also allow issues which "might take some time to be detected"
> too? It seems like the answer is, as always, that's what specs/tests are
> for.

Hm, not sure I agree.  With duck typing you will immediately know if
an object does not implement a required method.  Granted, you can pass
in all objects that satisfy the used contract without "noticing".  But
then again that's the whole point of duck typing. :-)  Maybe my
argument is not too important though.  The main point would be anyway
the first argument against, that then everything is Enumerable and the
module Enumerable basically becomes meaningless.

> One other thing that I thought of after my original email is that it might
> be preferable to change it to "yield self unless nil?", because it could be
> odd to have NilClass#each.

No.  You would simply use inheritance and implement a special version
in class NilClass which throws, e.g.

class NilClass
  def each
    raise NoMethodError, "undefined method `each` for %p" % self
  end
end

> Thanks for the thoughts!

You're welcome!  It's an interesting exchange.

Kind regards

robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/