From: Robert Klemme <shortcutter@...>
Date: 2010-01-20T18:54:12+09:00
Subject: Re: Looking for object.inherits?(Classname)

2010/1/20 Shot (Piotr Szotkowski) <shot@hot.pl>:
> Robert Klemme:
>
>> irb(main):010:0> a = []
>> => []
>
> […]
>
>> irb(main):015:0> Enumerable === a
>> => true
>
>> Note that I do not recommend using the test from line 12 as it is
>> likely much more inefficient than the other ones.  The test from line
>> 15 is especially suited for use with "case" statements as in
>
>> case a
>> when Enumerable
>>   puts "it's enumerable"
>> when Array, Hash
>>   puts "It's a special enumerable"
>> when Integer
>>   puts "You can count on me."
>> else
>>   puts "No idea about a."
>> end
>
> A minor nitpick: Note that due to case’s behaviour (once a ‘when’
> matches, other ‘whens’ are ignored), the above will almost never¹
> print ‘It's a special enumerable’, as Arrays and Hashes are almost
> always¹ Enumerable. Testing for Array/Hash first and Enumerable
> second would make more sense in most cases.

Oh, yes of course!  Thanks for catching that!  The order should have
been reversed.

case a
when Array, Hash
 puts "It's a special enumerable"
when Enumerable
 puts "it's enumerable"
when Integer
 puts "You can count on me."
else
 puts "No idea about a."
end

Thanks again!

Kind regards

robert

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