From: "David A. Black" <dblack@...>
Date: 2007-03-18T21:14:12+09:00
Subject: Re: const_missing - why is it necessary to hook it at Module?

Hi --

On 3/18/07, Clifford Heath <no.spam@please.net> wrote:
> Why doesn't the following code work?
>
> class Foo
>         def Foo.const_missing(sym)
>                 p sym
>                 sym.to_s
>         end
> end
>
> Foo.new.instance_eval {
>         Bar
> }
>
> I thought the missing constant Bar would be caught
> by the const_missing, since it's available on the
> class whose instance is being instance_eval'd.
>
> What gives? I'm writing a DSL and want to catch missing
> constants within a block being instance_eval'd

All that instance_eval does is set self and execute the block.
Constants don't depend on self for their scope; they use a kind of
quasi-static scoping, and the Bar in your block is resolved
(unsuccessfully) as Bar from the top level.

You'd need to add your const_missing method to Object, so as to cover
the top level.


David

-- 
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