From: Robert Klemme <shortcutter@...>
Date: 2008-02-24T05:24:58+09:00
Subject: Re: ||= [] idiom

On 23.02.2008 00:51, MenTaLguY wrote:
> On Sat, 23 Feb 2008 07:27:17 +0900, "Robert Klemme" <shortcutter@googlemail.com> wrote:
>> But all these points you mention do also apply to the Hash based
>> approach.  You can even use the same wording, if you like:
>>
>> @category_for = Hash.new {|h, tag| h[tag] = []}
> 
> Yes.  I was thinking in terms of why to do the refactoring at all,
> using my example refactoring as a point of reference, rather than
> weighing the pros and cons of different refactorings of the original
> code.
> 
>> I was expecting reasoning that would highlight advantages of using a
>> method here.  The only thing that comes to mind is that if you want to
>> exchange the implementation altogether, then a method based approach
>> is better.  But in that case you'd probably do
>>
>> def add_to_category(tag, item)
>>   (@cat[tag] ||= []) << item
>> end
>>
>> Because that abstracts away category creation *and* adding to the
>> structure.
> 
> This is a good point; I would prefer add_to_category to just category_for.
> 
>> On the flipside, for small scripts that Hash based approach has the
>> advantage of being shorter (because no method is needed).
> 
> True, though shorter isn't necessarily clearer.  One of the disadvantages
> of using default blocks for hashes is the additional cognitive burden when
> reading the code:  you must keep in the back of your mind that that, "this
> hash, it is a hash unlike any other."  I don't think that's a significant
> issue for small scripts, but it is why I tend to avoid the use of default
> blocks in larger scripts and libraries.

All good and valid points!  Thank you for this discussion!

Kind regards

	robert