From: Bruce Williams <bruce@...>
Date: 2002-12-06T18:34:16+09:00
Subject: Re: Printing subclasses

On Friday 06 December 2002 01:37 am, ted wrote:
| Can Ruby print the subclasses of a given class?  Like the reverse of the
| example of Class#superclass in "Reflection, ObjectSace and Distributed
| Ruby" in pickaxe.

Ted,

If you want a list of all subclasses of a certain class, you could implement 
something similar to the following:

	class SuperClass
		SUBS = []
		def Superclass.inherited subclass
			Superclass::SUBS << subclass
		end
	end

	class SubClass1 < SuperClass; end
	class SubClass2 < SuperClass; end

Due to the fact SuperClass.inherited is called for each definition of a 
subclass (with the subclass given as the argument), the contents of 
SuperClass::SUBS would then be: 

		[SubClass1, SubClass2]
	
I've seen this used for Plugin classes.

Note this approach does not require that the subclasses be instantiated; IIRC 
using ObjectSpace does.  Plus I think this is a little less-heavy handed.

Hope that helps,

~ Bruce

-- 
Bruce R. Williams :: [iusris/#ruby-lang] :: http://www.codedbliss.com

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