From: Daniel Brockman <daniel@...>
Date: 2005-07-15T11:29:12+09:00
Subject: Re: difference?

"Gene Tani" <gene.tani@gmail.com> writes:

> Hmm, seems to be few ways to test/monitor
> membership/inheritance/mix-in-ness:

Indeed. :-)

> Object#kind_of?, #is_a?,
>
> Module#ancestors,
>
> MyClassname === myobj

Interestingly, you've listed these in order of preference:

 * foo.kind_of? Foo                    --- perfect
 * foo.is_a? Foo                       --- unrubyish due to `is_*?'
 * foo.class.ancestors.include? Foo    --- long-winded and confusing
 * Foo === foo                         --- confusing and unnecessary

Of course, when checking multiple cases, this is perfect:

   case foo
   when Foo
     ...
   when Bar
     ...
   when Baz
     ...
   end

However,

> #instance_of?, #type (deprecated), #class

I'd order the ways of checking the exact class like this:

 * foo.class == Foo                    --- perfect
 * foo.instance_of? Foo                --- obscures the semantics
 * foo.type == Foo                     --- deprecated

> Module#included_modules, Class#inherited

(I left these out because they are normally useless, and primarily
serve as hooks to make obscure object-system hackery possible.)

In the same vein, there's alse Class#superclass.

-- 
Daniel Brockman <daniel@brockman.se>