From: Josh Cheek <josh.cheek@...>
Date: 2011-06-11T23:16:44+09:00
Subject: Re: a little challenge - reproduce this error

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On Sat, Jun 11, 2011 at 8:36 AM, Intransition <transfire@gmail.com> wrote:

>
>
> On Jun 10, 2:52 pm, Intransition <transf...@gmail.com> wrote:
> > On Jun 10, 1:19 pm, Josh Cheek <josh.ch...@gmail.com> wrote:
> >
> > > Well, I give up :)
> >
> > I bet a few people have come across it without fully knowing what was
> > going on and just fixed their issue by adding `::` to the "X". That's
> > what I did a few times before I realized what the hell was going on.
> >
> > The change needed to cause the error is this:
> >
> >     module X
> >       class Foo < BasicObject
> >         def call
> >           X
> >         end
> >       end
> >     end
> >
> > Right off you can see this only effect Ruby 1.9+ (b/c 1.8 has no
> > BasicObject).
> >
> > Next up... why it happens and how to fix.
>
> Ok, so the fix to this problem is... #const_missing:
>
>      module X
>        class Foo < BasicObject
>          def call
>            X
>          end
>          def self.const_missing(const)
>           Object.const_get(const)
>         end
>        end
>      end
>
> Which tells us why we get the error in the first place. Toplevel
> constants, like toplevel instance methods, are defined on Object
> itself -- the toplevel (aka `main`) is (mostly) just a proxy for
> Object. And since BasicObject doesn't inherit from Object like every
> other object in Ruby's universe, it can't find, in this case, module
> X.
>
> So that's the deal. If you ever run into this, you now know what to
> do.
>
>
Fascinating stuff!



> SIDE NOTE: I'm pretty sure that toplevel should not be a proxy of
> object. And that constant look up should terminate with the toplevel
> (just after Object) rather than with the Object class. A big benefit
> from this would be the ability eval scripts at the toplevel instead of
> in a protected module that emulated the toplevel (yet another proxy)
> in order to prevent method definitions from polluting every object. I
> mean think about that --every object. Talk about your monkey patching!
> I've mentioned this to matz before, and while he's never said as much,
> i'm hopeful that Ruby 2.0 (whenever that might arrive) will take the
> idea to heart.
>
>
I could see that. I already avoid defining toplevel methods, but when I do
make them, I usually make them on main's singleton class (unless, of course,
it really does need to be globally callable).


> P.S. In my attempt to "quizify" this Ruby quirk, I have to say, James
> Edward Gray II, I am humbled! :-)
>
>
lol.

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