From: Ben Bleything <ben@...>
Date: 2007-03-06T09:28:47+09:00
Subject: Re: nifty one-liner to search ObjectSpace?

On Tue, Mar 06, 2007, Giles Bowkett wrote:
> Say I've got a class and I know it has subclasses. I'm absolutely sure
> there must be an irb ObjectSpace one-liner to give me all the
> subclasses of an arbitrary class.

Yup :)

> I've been able to find the Class instance method #inherited(), which
> takes another class and tells you yay or nay, but a simple one-liner
> to return a class's subclasses has so far proved out of my reach.

ObjectSpace.each_object( Class ) {|klass| puts klass if klass < IO }

...will give you any class that is a subclass of IO.  Could pretty
easily be wrapped into a method you could call on a class.  In fact:

class Class
  def subclasses
    out = []
    ObjectSpace.each_object( Class ) {|k| out << k if k < self }
    return out
  end
end

Stick that in your .irbrc and call IO.subclasses.  YEAH.

> I know it exists. I just don't know what it is. I'm also kind of
> stymied because it appears ObjectSpace has #each_object but not #each.
> That seems so weird to me.

What would #each do that #each_object doesn't?

Ben