From: Quintus <sutniuq@...>
Date: 2010-08-06T18:25:27+09:00
Subject: Re: lt operator on class object, checking a class' superclasses

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Am 06.08.2010 10:57, schrieb Tomasz Wrobel:
> Hi!
> 
> Do you know a good way to check whether a class is a subclass of a
> certain class (given the class object, not an instance)?
> 
> one way would be to check all of klass.superclass,
> klass.superclass.superclass till nil
> 
> or klass.new.is_a?( cklass )
> 
> Accidentaly, I tried to such a operation:
> 
> klass < cklass
> 
> and it seems to work, but doesn't seem to be documented
> can somebody acknowledge this?
> 
> Best regards,
> Tomek W


It is documented, although it may be a bit hard to find, since the
behaviour is not defined in the Class class as one might expect, but in
it's superclass, Module. See the Module#<, Module#>, Module#<= and
Module#>= methods on http://www.ruby-doc.org/ruby-1.9/index.html . I'm
not sure what about Module#<=> since the docs say it works on mixins,
but it appears to work on classes as well.

Vale,
Marvin
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